# Triangle Teacher Resources

Find Triangle lesson plans and worksheets

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Lesson Planet

#### Getting into Trig

Starting with right triangles (SOH-CAH-TOA) and working up to the concept of radians, this collection introduces students to trigonometric ratios and supports them in learning to evaluate trigonometric functions.

Lesson Planet

#### EngageNY Grade 7 Math Module 6: Geometry

Twenty-seven lessons make up a math module designed for seventh graders to focus on the concept of geometry. Topics include angles, triangles, parallelograms, three-dimensional figures, and measurement using volume and area. Two...

Lesson Planet

#### Find the Area of Triangles, Quadrilaterals, and Polygons (6.G.A.1)

Before diving into the formulas for area, show where the formulas connect to the shape of the figure. The four videos look at different shapes and by decomposing them, they end up relating directly to their area formula.

Lesson Planet

#### Triangle Trade

Just a simple collection of unit segments to use when teaching about slavery. This will also help fight against common misconceptions of slavery in the west.

Lesson Planet

#### Common Core Math: 8th Grade

Check out the Common Core with a collection that represents all the 8th grade math standards. Most resources engage multiple standards but the main one is listed on the notes section of each tab.

Lesson Planet

#### EngageNY Grade 8 Math Module 3: Similarity

The concept of similarity is the focus of a module designed to boost eighth grader's math skills. Scholars examine the Fundamental Theorem of Similarity, dilations, and the Pythagorean Theorem. The module consists of 14 lessons and two...

Lesson Planet

#### Pythagorean Theorem: Not All Sides are Equal

You'll find fundamentals and advanced activities focused on the Pythagorean Theorem in this collection, which was designed for high schoolers but helpful for young geometrists of all ages!

Lesson Planet

#### Common Core Math: 6th Grade

Need some help aligning your 6th grade math curriculum to Common Core? Here is a collection complete with a resource for every standard in the curriculum. While many of these resources cover multiple math standards, the main one...

Lesson Planet

#### Algebra: High School Common Core Math

All Algebra, all the time! Here is a compiled list of resources that address all of the standards regarding Algebra Common Core for high school. Each resource has the main standard it addresses under the notes section of the item.

Lesson Planet

#### High School Math Handouts

A collection of different resources can augment any math curriculum. Sheets can be printed, posted on the wall, or emailed to students for use in the classroom.

EngageNY

#### EngageNY Grade 7 Math Module 3: Expressions and Equations

A math module challenges young mathematicians to generate equivalent expressions. Scholars demonstrate how order or grouping does not affect the practice of addition and multiplication. By the end of the module, learners recognize and...

Lesson Planet

#### "Grade 9-12, Claim 2 & 4: Problem Solving & Communication Reasoning Supports"

Small but mighty, a collection of three resources features presentation slides that prepare high schoolers for the Smarter Balanced assessment. Claim 2 features problem solving questions drawn from all content areas. Claim 3 focuses on...

Lesson Planet

#### Grade 8, Claim 1: Concepts and Procedures Item Slide Shows

Ten resources make up a collection of student and teacher-friendly slides that prepare eighth graders for the Smarter Balance assessment. Learners review rational and irrational numbers, convert repeating decimals to fractions, as well...

Lesson Planet

#### EngageNY Grade 6 Math Module 5: Area, Surface Area, and Volume Problems

Scholars take part in 20 lessons covering math concepts—area, surface area, and volume. Learning opportunities enforce knowledge of measurement and geometric shapes. A mid-unit exam challenges pupils to demonstrate what they know this...

Lesson Planet

#### EngageNY Grade 8 Math Module 2: The Concept of Congruence

Eighth graders delve deep into the concept of congruence with a 16-lesson math module. Lessons plans offer guided practice, inquiry-based learning opportunities, and independent practice. A mid-module assessment gauges progress while an...

Lesson Planet

#### Farm Printables Collection

Teach your class about the farm with the ABCmouse.com! This collection includes coloring pages, a word search, and color-by-numbers pages. Access these and thousands of other resources for Preschool through 2nd grade at...

Lesson Planet

#### Study Jams! Area of a Triangle

Even though there is a wide variety of different triangles in the world, knowing a single equation allows us to find the area of each and every one of them. Follow along with this step-by-step presentation as Zoe clearly models how to...

Lesson Planet

#### Lines of Symmetry for Triangles

What can symmetry tell us about triangles? After looking at four examples, learners will come to realize that lines of symmetry are different for equilateral, isosceles, and scalene triangles. Use this guided practice activity as an...

Lesson Planet

#### Triangle Area

While the lesson focuses on right triangles, this activity offers a great way to practice the area of all triangles through an interactive webpage. The activity begins with the class taking a square paper and cutting in in half; can they...

Lesson Planet

#### Frog Garden Party! Toads and Triangles in the Math Garden

It's frog party time! With frog banners, frog juice, and a triangle hunt, your garden party is sure to be both entertaining and educational. The lesson connects geometry, earth science, and delicious snacks to teach kids about ecosystems...

Lesson Planet

#### Two Triangles' Area

Need an activity for teaching the Pythagorean Theorem? Geometry juniors apply the Pythagorean theorem to two triangles to determine a final calculation.

Lesson Planet

#### What You Know About the Bermuda Triangle?

Get lost in the classifications. Using the backdrop of the Bermuda Triangle, pupils classify it by angle and side measures. They also learn information about the triangle and its history.

Lesson Planet

#### Find the Area of a Right Triangle

Help your class develop a greater understanding of the area of a right triangle. The video starts by reviewing the area of a rectangle and noting that the rectangle is made up of two congruent triangles. Learners are then shown that in...

Lesson Planet

#### Triangle Classification

Oh triangle, where are the points that will make your type? Given a line segment, pairs determine the location of a third point to create the six different types of triangles. The teacher provides a jumping off point by leading a...

Lesson Planet

#### Constructing SSS Triangles

Creating a triangles is as easy as 5, 6, 7. Using a ruler and compass to measure off lengths, a short video shows how to construct a triangle with three specific side lengths. The example creates a triangle with side lengths of 5 cm, 6...

Lesson Planet

#### Triangle Angle Sum

Don't believe everything that you hear — make them prove it! The video shows two methods to prove the Triangle Angle Sum Theorem. The following two videos apply the theorem to finding missing angle measures.

Lesson Planet

#### Constructing ASA Triangles

The narrator of a short video explains the steps in constructing a triangle given the measure of two angles and the length of the side between the angles. The resource provides opportunities for pupils to practice the skill with two...

Lesson Planet

#### Colorful Triangles

Learners examine a figure made up of different types of triangles and then determine whether each triangle is right, acute, or obtuse. Next, they color each type of triangle a different color. Finally, pupils answer three fill in the...

Lesson Planet

#### The Mathematical Secrets of Pascal’s Triangle

This modern animation and discussion of the ancient secrets of Pascal's triangle manages to be topical, engaging, and mathematically deep all at the same time. A great introduction to the power of number theory across multiple math...

Lesson Planet

#### Verifying Triangles are Congruent

Here the focus is on triangle congruence. Through an activity that requires investigation, questioning, and working together, geometers learn to identify corresponding parts of triangles to determine if the triangles are congruent....

Lesson Planet

#### Triangle's Interior Angles

Given a pair of parallel lines and a triangle in between, geometers prove that the sum of the interior angles is 180 degrees. This quick quest can be used as a pop quiz or exit ticket for your geometry class.

Lesson Planet

#### Classifying Triangles

If you're looking for a presentation to assist you in your teaching of triangles, this one could be for you. In it, learners are shown how triangles are classified by the size of their angles and by their sides. These are tricky concepts...

Lesson Planet

#### Triangles

After reviewing characteristics of seven types of triangles, young geometers discover how to find the missing angle of a triangle. Then, they practice identifying triangles, find missing angles, and find missing side lengths of similar...

Lesson Planet

#### How Do You Determine if a Triangle Is a Right Triangle if You Know its Sides?

Use the Pythagorean Theorem formula to check if this given triangle, with the given lengths of each side, is a right triangle. It's as simple as plugging the given values into the formula and doing the math to see if the solution checks...

Lesson Planet

#### Triangle Pack

With so many different types of triangles, it can be a challenge for young mathematicians to keep them all straight. Luckily this set of printable triangles is here to engage children in comparing and sorting triangles by their...

EngageNY

#### An Area Formula for Triangles

Use a triangle area formula that works when the height is unknown. The eighth installment in a 16-part series on trigonometry revisits the trigonometric triangle area formula that previously was shown to work with the acute triangles....

Lesson Planet

#### Mathematics Within: Slope and Triangles

Learners discover a method for determining the slope of a line by creating and comparing similar triangles. They fold coordinate grids to make three similar triangles then measure the sides to compare the relationships between the...

Lesson Planet

#### Right Triangles Inscribed in Circles II

So many times the characteristics of triangles are presented as a vocabulary-type of lesson, but in this activity they are key to unraveling a proof. A unique attack on proving that an inscribed angle that subtends a diameter must be a...

EngageNY

#### The Angle-Angle (AA) Criterion for Two Triangles to Be Similar

What do you need to prove triangles are similar? Learners answer this question through a construction exploration. Once they establish the criteria, they use the congruence and proportionality properties of similar objects to find...

Lesson Planet

#### Interior Designers: Working with Right Triangles

Adding a career application, the resource explores the idea of making squares from the sides of a right triangle to show that the sums are equal. The question refers to designing a mural that leads the class into their own drawing of a...

Lesson Planet

#### Triangles

What has three sides and is adorable? A-cute triangle. The resource introduces triangles and how to classify them by sides and angles or both. The video concludes with using the sum of the angles of a triangle to show how to solve for a...

Lesson Planet

#### Classifying Triangles: Lesson

That's correct, it is right and scalene. The video introduces the two methods for classifying triangles, sides, and angles. A resource in the playlist for basic geometry provides the definitions for each of the classifications.

Lesson Planet

#### Equilateral Triangles: Lesson

Take a second look at triangles that are equal all the way around. The video reminds viewers what an equilateral triangle is and points out that the three angles are the same. Using the fact that equilateral triangles are also isosceles,...

Lesson Planet

#### Similar Triangles and Linear Functions

What do similar triangles have to do with linear equations? Building on prior knowledge of similar triangles, learners discover that the slope of the sides of similar triangles is the same. They make their discoveries while graphing...

Lesson Planet

#### Similar Right Triangles and Trig Ratios

Is it possible to be the same yet different? Absolutely! The activity asks learners to explore the relationships between side ratios of triangles they have drawn. Because individuals all draw a triangle with the same angle measures, they...

Lesson Planet

#### 45-45-90 Triangles

45-45-90 triangles are half a square, which gives them a special status! The instructor explains the relationship of the sides of the 45-45-90 triangle using the Pythagorean Theorem as a reference.

Lesson Planet

#### Lyle's Triangles

Try five problems on triangles. Levels A and B focus on shapes that can be created from right triangles. Level C touches upon the relationship between the area of a six-pointed star and the area of each triangle of which it is composed....

Lesson Planet

#### Congruent Triangles: Lesson

Given two congruent triangles, the resource provides the definition of congruent triangles and marks the corresponding parts. The portion of a basic geometry playlist shows the triangles are congruent by moving one on top of the other...

Lesson Planet

#### Comparing Triangle Angles and Sides: Lesson

Use the opposite to organize angles or sides. The video provides the relationship of angle measures based on the lengths of sides in a triangle and its converse. Using two triangles, the segment of a larger playlist on geometry shows the...

Lesson Planet

#### Triangle Inequality Theorem: Lesson

Can any three lengths make a triangle? One of the videos in a playlist on basic geometry introduces the Triangle Inequality Theorem. Using three given lengths, the presentation illustrates the restrictions on lengths of any side of a...

Lesson Planet

#### Area and Perimeter of Triangles: Lesson

Go from a parallelogram to a triangle. A segment of an extensive playlist on basic geometry shows the derivation of the formula for the area of a triangle. The resource works examples that require finding a missing side or height to...

Lesson Planet

#### Triangle Sum Theorem: Lesson

The measures all add up. The presentation, part of a helpful playlist on geometry, provides the statement of the Triangle Sum Theorem. Using the theorem, the video shows how to find the missing measure of an angle.

Lesson Planet

#### Isosceles Triangles: Lesson

Two sides give us two angles. A segment of a playlist on basic geometry revisits isosceles triangles. The presentation explains several properties and theorems related to isosceles triangles.

Lesson Planet

#### SAS Triangle Congruence: Lesson

SAS is not just a spy organization. A section of an extensive geometry playlist introduces a way to show two triangles are congruent, SAS. Using diagrams, the video provides an explanation by showing only one triangle is formed with two...

Lesson Planet

#### Special Right Triangle 45-45-90: Lesson

Square roots connect squares and right triangles. Using the Pythagorean Theorem, the video shows the relationship between the sides and hypotenuse of a 45-45 right triangle. The portion of a larger geometry playlist applies the...

Lesson Planet

#### Triangle Proportionality: Lesson

Look at proportionality from a parallel perspective. A section of an expansive geometry playlist introduces the Triangle Proportionality Theorem. Using the theorem, the video shows how to determine missing measurements in triangles.

Lesson Planet

#### Similar Triangles

Are they similar? The lesson provides an explanation of the angle-angle criterion for triangle similarity. Several problems allow the class to determine whether the two triangles with the given angle measures are similar or not.

Lesson Planet

#### Pythagorean Theorem for Solving Right Triangles: Solving the Triangle

Observe the change in the trigonometric ratios as angles vary. An interactive provides the values of trigonometric ratios for both acute angles in a right triangle. Pupils create a right triangle to match given criteria and find the...

Lesson Planet

#### Classify Triangles - Homework 15.3

Elementary schoolers identify triangles as equilateral, scalene, isosceles, or right. Seven triangles are depicted for them, followed by two word problems. This would serve best as a homework or an assessment.

Lesson Planet

#### Finding the Area of an Equilateral Triangle

The problem seems simple: find the area of the equilateral triangle whose sides are each length 1. In fact, this same problem is solved in 8th grade, addressing a different Common Core standard, using the formula for area of a triangle...

Lesson Planet

#### Toothpick Triangles

Students draw a chart (included in the lesson) to use with their investigation. They review terminology of triangles and receive toothpicks to use in the lesson. Beginning with three toothpicks, students form a triangle. They complete...

Lesson Planet

#### Identifying a Triangle by its Sides and Angles

Identify triangles by their angle measures and side lengths by looking at and measuring angle measures and side lengths. Use Cabri Jr. to construct various triangles, then manipulate the construction to create the 6 types of triangles,...

Lesson Planet

#### Triangle Sum Theorem

Your visual geometry learners will appreciate triangle drawings as they model the triangle sum theorem and algebraically solve to find the missing interior angle in a triangle. Practice problems increase in complexity and vary in their...

Lesson Planet

#### Triangles

Why are there so many different types of triangles? Be that as it may, beginning geometers need to understand the differences between equilateral, isosceles, scalene, and right triangles, and they get a visual approach with this...

Lesson Planet

#### Best Triangle

What makes an equilateral triangle equilateral? It turns out it's much more than just the side lengths! Learners analyze four different triangles to determine the best equilateral triangle. They create a formula that they later use to...

Lesson Planet

#### Exploring Triangle Proportions

Students identify similar triangles. In this exploring triangle proportions lesson, students examine similar triangles. They determine the length of missing sides and angle measurements. Students use the Cabri Junior to draw and...

Lesson Planet

#### Triangle Designs - Enrichment 16.5

Upper graders cut out cards with the scalene, isosceles, equilateral, acute, obtuse, and right triangle terms, choose a card, and complete the chart with the number of sides or angle and draw the design. They complete one chart.

Lesson Planet

#### Slope/Triangle Area Exploration

Using CAS TI-Nspire, explore how the area of a triangle formed by the x- and y-axes and a line through a point is related to the slope of a line. Additionally, the activity serves as an introduction to rational functions and the concept...

Lesson Planet

#### Draw Triangles Using Given Angles

Middle schoolers are given set angles and asked to draw a complete triangle by using a protractor. Watch how the narrator walks through each measure and line to finish with an isosceles triangle.

Lesson Planet

#### The Pythagorean Theorem and Classifying Triangles

Through the examination of the relationship between the lengths of the sides of a triangles students will learn the classification of triangles (acute, right, or obtuse).

Lesson Planet

#### Area of a Triangle

Base times height or one half base times height ... area formulas are pretty predictable! Given the base and height dimensions of a triangle, a video lesson explains the process of finding the area. Learners have the opportunity to...

Lesson Planet

#### Congruent Triangles

Young mathematicians learn about the many theorems related to congruent triangles. The video allows them to stop and replay the content as many times as needed to take notes. Extra practice problems work as reinforcement for each skill...

Lesson Planet

#### 45-45-90 Triangles

The process for calculating values using a right triangle with angles of 45 degrees is covered in this third portion of the Pythagorean Theorem series. Here, Sal uses algebra to calculate the value of an angle. The solution to the sample...

Lesson Planet

#### Intro to 30-60-90 Triangles

As the fourth part of a series on the Pythagorean Theorem, Sal continues an exploration of the ways to calculate the length of sides of a right triangle using algebra. He also explores using this theorem to solve problems involving a...

Lesson Planet

#### Theorems of Triangles

Show your school spirit while proving theorems about triangles! Your student geometers are charged with coming up with a new design for the school pennant, following specific guidelines. Along the way, they need to prove the theorem that...

Lesson Planet

#### Intro to 30-60-90 Triangles

Lesson Planet

#### 45-45-90 Triangles

Lesson Planet

#### 30-60-90 Triangles All

Using this video, which is the fourth in a series, the instructor continues a discussion involving the Pythagorean theorem. This video focuses on calculations involving right triangles with 30 and 60 degree angles.

Lesson Planet

#### Geometry Practice: G.G.28 #1: Congruent Triangles

In this congruent triangles worksheet, students solve four multiple choice problems. Students determine which statement is the appropriate reasoning to say that two triangles are congruent.

Lesson Planet

#### How Do You Find the Angles in a Triangle if You Have a Ratio of Their Measures?

Use the Triangle Sum Theorem to find the value of each of the inside angles of a triangle. This triangle problem has to do with the ratio of the angles to each other. Find the measure of each angle if the ratio is 1:3:8. Not sure how to...

Lesson Planet

#### Triangles

This unit enables scholars to apply the rule for area of a triangle (area equals half base times height). They practice multiplication and division strategies as they calculate areas.

Lesson Planet

#### What is the Triangle Sum Theorem?

If you add the value of the three interior angles in a triangle will it equal 180 degrees? Yes it will. The instructor illustrates and proves the Triangle Sum Theorem. Follow closely as she explains her proof.

Lesson Planet

#### Counting Triangles

Help your little learners recognize number words one through ten. Each slide contains a triangle with a number word inside of it. As the slides progress, more triangles appear in successive order 1-10. This is a great way to reinforce...

Lesson Planet

#### Study Jams! Classify Triangles

Jam on with this multi-faceted activity teaching triangle classification. Start with a learner-paced lesson describing the different qualities of triangles and follow with a fun karaoke session. Also provided are two types of...

Lesson Planet

#### Terrific Triangles

Scholars show what they know about types of triangles with a hands-on activity that challenges them to build models using toothpicks. Following a whole-class discussion and brief presentation, small groups gather to form shapes and...

Lesson Planet

#### Triangles and Angle Sums - Homework 14.5

Upper elementary and middle school learners solve four problems where they are given two angle measurements in a triangle and must calculate the measurement of the third angle. They are given a diagram and find the measurement of six...

Lesson Planet

#### Triangle Area Patterns

Combine algebraic and geometric strategies to find solutions. The task asks learners to find the coordinates of a third vertex of a triangle to create a triangle with a specific area. The project is a set of seven problems that helps...

Lesson Planet

#### Isosceles Triangle Spaces

How many different types of triangles can your class name? A discovery lesson guides learners through an exploration of the different triangle types and the relationships between their angles and sides. Using coordinate geometry,...

Lesson Planet

#### Classifying Triangles

Bring math and reading informational text together with a reading comprehension lesson. After kids read about isosceles, scalene, and equilateral triangles, they answer five comprehension questions to demonstrate how they can use context...

EngageNY

#### Special Relationships Within Right Triangles—Dividing into Two Similar Sub-Triangles

Why are right triangles so special? Pupils begin their study of right triangles by examining similar right triangles. Verifying through proofs, scholars recognize the three similar right triangles formed by drawing the altitude. Once...

EngageNY

#### The Area of Acute Triangles Using Height and Base

Use the height of an acute triangle to create two right triangles. The third lesson in a series of 22 has pupils divide acute triangles into two right triangles. Scholars calculate the areas of the two right triangles and add them...

Lesson Planet

#### The Sum of Angles in a Triangle

An informative lesson contains a brief explanation of how the sum of the angles of a triangle is a line. The lesson continues with determining the missing angle in a triangle, or solving for a variable. Using the sum of the angles, the...

EngageNY

#### Conditions for a Unique Triangle—Three Sides and Two Sides and the Included Angle

Building on the previous activity in the 29-part series, the ninth activity asks individuals to construct a triangle given specific criteria. First, they are given three specific side lengths and then two sides and the included angle....

EngageNY

#### Drawing Triangles

Create concrete examples of triangle congruence for your classes. The eighth installment of the 29-part module sets the stage for studying triangle congruence. Given a set of criteria, math scholars use constructions to build a triangle....

EngageNY

#### Checking for Identical Triangles

Examine an assortment of triangle congruence criteria in a single lesson. Building on the four previous lessons of the series, the 13th installment provides a mixture of the different triangle congruence criteria for pupils to identify....

Lesson Planet

#### How Many Triangles?

Something for young mathematicians to remember: the sum of any two sides must be greater than the third. Class members investigates the Triangle Inequality Theorem to find the relationship between the sides of a triangle. At the same...

Lesson Planet

#### Special Right Triangles and Right Triangle Trigonometry

Right triangles are so special! Use special right triangles to discover the trigonometric ratios. Pairs construct special right triangles and find the values of the ratios of the sides. In the process, they discover the ratios stay the...

EngageNY

#### Identical Triangles

Explore vocabulary and notation related to triangles and congruence. The fifth lesson in the 29-part series helps pupils build their knowledge of triangle relationships. Individuals identify corresponding parts of identical triangles and...

EngageNY

#### Conditions on Measurements That Determine a Triangle

Can any three side lengths create a triangle? Your classes tackle this question and more in the 11th lesson plan of the 29-part module. Through modeling with patty paper, individuals discover the relationship between the lengths of the...

EngageNY

#### Checking for Identical Triangles II

Given a diagram of connected or overlapping triangles, individuals must find congruent parts by using various properties. Pictures include reflexive sides and vertical angles amongst the marked congruent parts.

EngageNY

#### The Area of All Triangles Using Height and Base

Drop in the altitude is all that is needed. Pupils explore finding areas of different types of triangles. Learners realize the formula for finding their area is the same and explore the location of altitudes in triangles to finish the...

EngageNY

#### Unique Triangles—Two Sides and a Non-Included Angle

Construct an understanding of triangle congruence through a visual analysis. Young scholars find that given two sides and a non-included angle sometimes produces two possible triangles. Their analysis continues to show that if the...

Lesson Planet

#### If at First You're Not the Same, Try Triangles! (Part 1)

Congruent sides + congruent angles = congruent triangles. Scholars first create several triangles that satisfy given conditions using straws. They investigate the triangles to see which are congruent, and then they define what it means...

Lesson Planet

#### Triangle Inequality

This STEM lesson plan presents a guided inquiry-based activity on exploring the relationship between the side lengths of a triangle. Class members are encouraged to also find the relationship between angle measure and side lengths....

Lesson Planet

#### Similar Triangles

Pupils work in pairs to investigate what it takes to prove that two triangles are similar. They work through various shortcuts to find which are enough to show a similarity relationship between the triangles. Small groups work with the...

Lesson Planet

#### Triangle Congruence with Rigid Motion

Combine transformations and triangle congruence in a single lesson. Scholars learn to view congruent triangles as a rigid transformation. Using triangle congruence criteria, learners identify congruent triangles and the rigid...

Lesson Planet

#### Similar Triangles

Proving triangles are similar is often an exercise in applying one of the many theorems young geometers memorize, like the AA similarity criteria. But proving that the criteria themselves are valid from basic principles is a great...

EngageNY

#### Perimeter and Area of Triangles in the Cartesian Plane

Pupils figure out how to be resourceful when tasked with finding the area of a triangle knowing nothing but its endpoints. Beginning by exploring and decomposing a triangle, learners find the perimeter and area of a triangle. They then...

EngageNY

#### Special Lines in Triangles (part 1)

Allow your pupils to become the mathematicians! Individuals explore the properties of a midsegment of a triangle through construction and measurement. Once they figure out the properties, learners use them to draw conclusions.

EngageNY

#### Special Lines in Triangles (part 2)

Medians, midsegments, altitudes, oh my! Pupils study the properties of the median of a triangle, initially examining a proof utilizing midsegments to determine the length ratio of a median. They then use the information to find missing...

EngageNY

#### Congruence Criteria for Triangles—AAS and HL

How can you prove it? Guide classes through an exploration of two possible triangle congruence criteria: AAS and HL. Learners connect this criteria to those previous learned and also explore criteria that does not work. The lesson...

EngageNY

#### More About Similar Triangles

Determine whether two triangles are similar. The lesson presents opportunities for pupils to find the criterion needed to show that two triangles are similar. Scholars use the definition of similarity to find any missing side...

Lesson Planet

#### Congruent Triangles

Is this enough to show the two triangles are congruent? Small groups work through different combinations of constructing triangles from congruent parts to determine which combinations create only congruent triangles. Participants use the...

Lesson Planet

#### Investigating Similar Triangles

Let your use of the resource be in proportion to its usefulness. Pupils investigate similar triangles by measuring side lengths and considering given angle measures. The results of the investigation help develop generalizations about...

Lesson Planet

#### "Triangle Congruence Show" Starring Rigid Transformations

Understand congruent triangles using transformations. The lesson introduces the concept of using rigid transformations to show that two triangles are congruent. Pupils use patty paper and other tools to develop the concept before showing...

Lesson Planet

#### Writing Task 6.G.3 Item 2

Donnie and Steward each created triangles on a coordinate plane and want to know if they have the same area. Young mathematicians use their ability to plot ordered pairs and find the area of triangles to help answer this...

Lesson Planet

#### Joining Two Midpoints of Sides of a Triangle

Without ever using the actual term, this exercise has the learner develop the key properties of the midsegment of a triangle. This task leads the class to discover a proof of similar triangles using the properties of parallel lines cut...

Lesson Planet

#### 30-60-90 Triangles

Half of an equilateral triangle is a special right triangle. A video instructor shows how to find the pattern of the side lengths for a 30-60-90 triangle. She then applies the relationship to different examples.

Lesson Planet

#### The Triangle, Circle and Square

Get to know the triangle, circle, and square with a music video filled with hand-drawn animation set to a laid back beat.

Lesson Planet

#### Isosceles Triangles on a Geoboard

How many isosceles triangles can you create on a seven-by-seven peg board? This is the task scholars attack in their collaborative groups. The problem prompts discussion on distance, slope, and the definition of isosceles triangles.

Lesson Planet

#### Finding Triangle Vertices

Where in the world (or at least in the coordinate plane) is the third vertex? Given two coordinate points for the vertices of a triangle, individuals find the location of the third vertex. They read an account of fictional...

Lesson Planet

#### Inscribed Similar Triangles: Lesson

Create similar triangles with a little altitude. A section of an extensive playlist on basic geometry discusses how an altitude of a right triangle creates similar triangles. Using the theorem, the presentation finds unknown side...

Lesson Planet

#### Area of a Triangle

Triangles are not all created the same. The instructor shows how to find the area of different types of triangles using the formula. She also includes an example requiring coordinate geometry.

Lesson Planet

#### HL Triangle Congruence: Lesson

Use the right congruence statement. The video introduces the Hypotenuse-Leg Theorem to prove two right triangles are congruent. Part of a geometry playlist shows that it does not matter which leg to use when proving congruence.

Lesson Planet

#### Similar Triangles 1

Find two similar triangles in plane sight. Given a figure composed of a parallelogram and a triangle, pupils identify two similar triangles and provide an explanation. Class members use the similar triangles to find two missing side...

Lesson Planet

#### Squaring the Triangle

Teach budding mathematicians how to square a triangle with an interactive that shows a graphical proof of the Pythagorean Theorem. Pupils alter the lengths of the legs using sliders. Using the inputted lengths, the applet displays the...

Lesson Planet

#### Triangle AA Similarity: Lesson

Two sets of congruent angles leads to three. Using diagrams of two triangles, the presentation intuitively shows that if two sets of angles are congruent, the third set is too. The portion of a geometry playlist uses that information to...

Lesson Planet

#### Perimeter and Area of a Right Triangle

Make sure the coordinates are right when calculating distances. Given a right triangle on the coordinate plane, pupils determine the perimeter and the area. The scholars calculate the length of each side using the coordinates of the...

Lesson Planet

#### SSS Triangle Congruence: Lesson

Gimme three sides, mister! The video introduces the Side-Side-Side Triangle Congruence Theorem. Using segments of different lengths, the portion of a larger playlist on geometry shows that only one triangle can be built.

Lesson Planet

#### Special Right Triangle 30-60-90: Lesson

It is special—given one length, you can find the other two. A segment of a basic geometry playlist provides the ratio of the lengths of sides of a 30-60 right triangle. The presentation shows how to use the ratio to find side lengths...

Lesson Planet

#### The Measure of an Angle of a Triangle

Assess your class' knowledge of triangle properties. Scholars interpret given information to determine how to find the measure of an unknown angle. The resource provides all information in the directions with the expectation that...

Lesson Planet

#### How Do You Find Missing Angles in a Triangle With Variables?

Are you working on finding the missing angles in triangles in your class? Consider this video. An instructor uses the triangle sum theorem to create an equation that helps her find the missing angles. She explains each step and writes...

Lesson Planet

#### Discovering the Formula for the Area of a Triangle

Most high schoolers are very familiar with the area of the triangle being equal to 1/2 base times the height. Here, they will develop and test their formula for the area of a triangle when given two adjacent sides and the included angle....

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#### Acute Triangles

Learners study acute triangles. They measure angles using a protractor, then classify the triangles as either right, obtuse, or acute. Everyone creates a design for a Navajo rug using only acute triangles.

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#### Different Types of Triangles

Are there different types of triangles? Yes there are, and this presentation describes each by its properties or characteristics. Right, equilateral, isosceles, and scalene are all shown and defined. The presentation isn't particularly...

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#### Study Buddies: Classifying Triangles

In this math worksheet, young scholars analyze an informative chart about the measurement and angles of equilateral, isosceles and scalene triangles. Students then answer 5 questions about classifying triangles.

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#### Triangle Designs

In this triangles worksheet, students draw different triangles and write how many sides and angles each one has. Students draw 4 kinds of triangles and have 2 that are impossible to draw.

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#### Exploring Congruent Triangles

In this congruent triangles learning exercise, students solve 12 different equations related to writing a correspondence statement for triangles in the given diagrams. They complete each correspondence statement and write a congruence...

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#### Geometry/Triangles

Middle schoolers cut out triangles and sort them according to angles. In this triangles lesson, students classify triangles according to the angles and sides. They make a study guide to assist in remembering the types of triangles....

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#### Triangles

In this triangles worksheet, 4th graders study the lengths that are stated for 3 triangles and describe each triangle by its sides. Students describe 3 additional triangles by their angles.

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#### Types of Triangles and Coordinate Grids

Students begin the lesson plan with a review of the different types of triangles. As a class, they are introduced to the coordinate system and participate in game in which they find different coordinates. They must knock out as many...

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#### Unit 5: Worksheet 3 - Similar Triangles

In this similar triangles worksheet, students use proportions to solve for the missing sides of similar triangles. This two-page worksheet contains 16 multi-step problems.

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#### Classify Triangles

Here is a classifying triangles practice worksheet in which learners sharpen their problem solving skills as they solve six story problems.

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#### Courting Shapes-Triangles and Diamonds

A counting shapes learning exercise on which kindergarteners color triangles pink and diamond blue. They count the number of each shape and write it down. There are seven diamonds and eight triangles to count.m

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#### Classifying Triangles

Building on young mathematicians' prior knowledge of three-sided shapes, this lesson series explores the defining characteristics of different types of triangles. Starting with a shared reading of the children's book The Greedy Triangle,...

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#### Classifying Triangles

Young mathematicians explore the world of three-sided shapes in this lesson on the different types of triangles. Starting with a general introduction to classification using Venn diagrams, children learn how to categorize triangles based...

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#### Pythagorean Theorem to Classify Triangles: Missing Angles

Learn to use the Pythagorean Theorem with non-right triangles. Pupils use the interactive to discover the relationship between the lengths of sides for acute and obtuse triangles. They compare the squares of the sides of the triangles to...

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#### Lengths of Sides in Isosceles Right Triangles: Paper Football

Fuse sports and geometry by having your class create paper footballs—that are actually isosceles right triangles! Scholars use an interactive to create an isosceles right triangle to model a paper football. From the information in the...

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#### Triangles and Midpoints

Here are two tasks for a three-sided figure. Scholars complete some problems given a triangle. The first is to show that a quadrilateral drawn with midsegments of the triangle is a parallelogram. The second is to find the perimeter of...

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#### Lengths of Triangle Sides Using the Pythagorean Theorem: Find the Missing Side

What is the relationship between the sides of a right triangle? Learners use an interactive to create models of right triangles and view the relationship between the lengths of the sides. They finish by using the Pythagorean Theorem to...

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#### Relationships of Sides in 30-60-90 Right Triangles: Truck on a Mountain Road

Determine the change in elevation on a mountain road. Individuals use the interactive to simulate a truck driving up a mountain road with a 30-degree incline. They determine missing sides of a 30-60 right triangle to find horizontal and...

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#### Perimeter and Area of an Obtuse Triangle

Make a coordinated effort to draw an altitude. Using an obtuse triangle plotted on a coordinate plane, scholars determine the perimeter and area of the triangle. after determining the lengths of the sides using the coordinates, learners...

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#### Showing Triangles Congruent Using Rigid Body Motion

Coordinate using transformation in congruence proofs. An assessment provides pupils with two triangles on the coordinate plane. Relying on known information about rigid transformations, scholars describe the transformations necessary to...

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#### Interpreting Characters, Setting, Plot, and Theme - The Triangle Shirtwaist Factory Disaster

Examine story development and historical disaster with your class. Learners view a video depicting the incidents surrounding The Triangle Shirtwaist Disaster. They use graphic organizers and the Internet to gather enough information to...

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#### Alternate Formula for the Area of a Triangle: Alternate Area of a Triangle

It's always nice to have a plan B. Pupils investigate an alternate formula for the area of a triangle that uses sine. A set of challenge questions shows how the new formula relates to the well-known formula of (1/2)bh.

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#### Pascal's Triangle: Pyramid Blocks

Build a pyramid of sums. An interactive presents the first five rows of Pascal's Triangle as a pyramid. Pupils match missing entries in the pyramid and continue the pattern to determine entries of other rows. The learners use the entries...

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#### Similar Triangles

Although a rather complicated topic, this video manages to clearly explain the concept of solving problems involving similar triangles. It employs problem solving to determine whether two figures are similar triangles. In addition, it...

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#### Similar Triangles (Part 2)

Building on concepts in the first part of the series on similar triangles, installment number two explores how to find the values for given angles in a triangle. These problems are solved by using algebra and ratios. A step-by-step...

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#### Inequalities in a Triangle

Stuck with triangle proofs? Take a 180° and provide learners with a guided worksheet that tests their knowledge with triangle inequalities. The questions require different types of proofs that range in levels of difficulty.

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#### Circus of Shapes: Triangles

Guide your class in learning the triangle with this coloring worksheet. Learners identify triangles among a variety of different shapes and color in each triangle. This worksheet has color pictures in a circus theme that makes it more...

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#### Area of a Triangle: Formula

Determine the area of a triangle using the formula 1/2L x H. The formula is shown then demonstrated on both regular and irregular triangles. There are five practice problems included.

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#### Telly Plays The Triangle

Big Bird gives Telly a lesson on living vs. non-living things in this film. Telly is afraid to play a musical instrument, a triangle, he is holding because he thinks he might hurt it. After Big Bird tells Telly the triangle isn't living,...

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#### Triangles

In this triangles worksheet, 10th graders solve 3 extensive informal geometry problems that involve triangles. First, they sketch a triangle, selecting 3 of the sides and constructing 3 midpoints. Students then draw each of 3 medians by...

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#### Pythagoras Rectangles and Isosceles Triangles

When does the Pythagorean Theorem come in handy? An intriguing video uses the Pythagorean Theorem to solve problems other than simply finding the length of a side of a right triangle. Pupils find the diagonal of a rectangle and the...

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#### Constructing Equilateral Triangles and 60 Degree Angles

Creating a 60-degree angle also creates an equilateral triangle. By watching the video, individuals learn the steps required to construct a 60-degree angle. The presentation shows that the process is the same for constructing an...

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#### Showing a Triangle Is Right Angled

Determine whether it is right or not. Using the Pythagorean Theorem, the video shows how to determine whether a triangle is a right triangle. Pupils practice the skill in a few of the problems in the associated worksheets on the...

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#### Classify Triangles - English Learners 16.5

In this classifying triangles worksheet, learners solve four multiple choice problems where they classify triangles as scalene, right, isosceles, and equilateral.

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#### Triangles and Congruence

Can your class construct triangles and determine congruence? Find out with this well put together worksheet. THey construct triangles to given specifications and identify if they are congruent. There are 3 muti-step problems to solve.

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#### 45-45-90 Triangles

In this geometry worksheet, 10th graders use right triangle trigonometry to solve problems involving 45â—¦-45â—¦-90â—¦ triangles. The three page worksheet contains twenty problems.

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#### Area of a Triangle – Sine/Trigonometry

Half the base times height was great for elementary school, but now we have a more general formula. Scholars watch a short video that highlights the area formula A = 1/2 ab sin C. The narrator works through an example of applying the...

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#### Identifying Similar Triangles

Math whizzes work with angle sums and exterior angles to figure out the measure of other angles. This particular publication provides comprehensive support in the form of an anticipatory activity, questions designed to prompt discussion,...

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#### Alice in Fractalland

Take your class on a field trip to Fractalland where they'll learn all about number and shape patterns. Based on Disney's movie Alice in Wonderland, this resource takes young mathematicians on an adventure as they explore patterns in...

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#### Special Right Triangles

Using the Pythagorean Theorem to solve for missing angles, learners evaluate right triangles and their properties.

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#### Triangle Sum

Explore, investigate, and finally prove the angles in a triangle have a sum of 180 degrees. Young geometers use the Interior Angles Theorem, and properties and definitions of congruency.

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#### Congruent Triangles

Geometers prove that triangle PQR is congruent to triangle ABC by describing any combination of rotations, reflections, and translations that would prove it so. There is only this single task on the handout, but a detailed explanation of...

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#### Investigating the Properties of the Centroid of a Triangle

Your geometry learners will use dynamic geometry software to find the centroid of a triangle. Then they will play a game to find the balancing point of a triangle and compare it to the centroid..

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#### Triangle Congruence with Coordinate

Two triangles are displayed on a coordinate plane. Youngsters apply a reflection and a translation to demonstrate their congruence. This exercise makes a terrific tool for teaching these concepts, or a way to assess learning.

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#### ASA and AAS Triangle Congruence Lesson

The location of the side makes a difference. One of the videos in a geometry playlist introduces angle-side-angle and angle-angle-side congruence relationships. Using drawings, the video shows how these two congruence statements are...

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#### Area of Diagonal Generated Triangles of Rectangle are Equal

Finding the area of each of the triangles that are created by drawing two diagonal lines through a rectangle is explored in this lecture. It provides a detailed explanation of how to use a formula to solve the given problem. Tip: Use...

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#### Area of Diagonal Generated Triangles of Rectangle are Equal

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#### Constructions Triangles

Learners explore the difference between a construction and a drawing. They focus on various ways to construct different types of triangles. The lesson is an application of Cabri Jr. and reinforces the difference between a constructions...

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#### SAS Triangle Congruence

Students investigate proving two triangle congruent using SAS triangle congruence. For this SAS triangle congruence lesson, students use Cabri Jr. to construct triangles two congruent triangles. Students prove the triangles are...

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#### ASA Triangle Congruence

Young scholars explore the concept of congruent triangles. In this congruent triangles activity, students use Cabri Jr. and their graphing calculator to determine if two triangles are congruent by the ASA triangle postulate. Young...

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#### Ratios of Right Triangles

Learners find the angle measures of a right triangle given two side lengths. In this finding the angle measures of a right triangle given two side lengths lesson, students record the ratio of a leg and hypotenuse of a right triangle. ...

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#### Chapter 8 Extra Problems Worksheet: Similar Triangles

For this similar triangles worksheet, high schoolers solve 6 similar triangles. Students use proportions to solve similar triangles and similar rectangles.

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#### Practice 5-1 Midsegments of Triangles

For this midsegment of triangles worksheet, students find the midsegment of a line in triangles and quadrilaterals. They identify parallel segments in diagrams and find the bisectors in triangles. This two-page worksheet contains a total...

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#### Triangle Similarity

In this triangle similarity worksheet, 10th graders solve and complete 12 different problems that include defining similar and 3 similar statements using only sides and angles. First, they determine if each pair of triangles shown are...

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#### Triangle Properties

Students explore parts of triangles. In this triangle properties lesson, students examine the relationship between the legs and the hypotenuse of a triangle. They use models of triangles to examine the Pythagorean Theorem. Students...

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#### Similar Triangles

Students investigate the difference between similar and congruence. In this geometry instructional activity, students examine triangles and polygons and define what makes one congruent and what makes one similar, but not congruent.

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#### Kuta Software - Infinite Geometry: Similar Triangles

In this similar triangles worksheet, students solve 20 short answer problems. Students determine if two given triangles are similar. Students determine the type of similarity given two triangles. Students are given a sketch of the...

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#### Nested Similar Triangles

Nested triangles have been created so that they share a common vertex and vertex angle. Learners drag the endpoints of the side that is opposite the common angle to discover the conditions that make the nested triangles similar. When...

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#### Investigating Segments in a Triangle

Pupils investigate segments in a triangle by constructing a triangle using Cabri Jr. They construct segments within the triangle that lie on the midpoints of the triangle's sides. Learners then compare the slope of base of the triangle...

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#### Measuring Angles in a Triangle

High schoolers investigate the sum of the measures of the angles of a triangle. They draw a triangle and measure the interior angles. Using Cabri Jr., learners find the sum of the measures of the interior angles. The lesson provides an...

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#### Circumscribing a Circle About a Triangle

Pupils circumscribe a circle about a triangle. They construct a triangle using Cabri Jr and then circumscribe it. They then use knowledge of perpendicular bisectors and circumcenters to locate the center of the circle and then...

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#### Midsegments of a Triangle

Students analyze midsegments of triangles in this lesson. They use Cabri Jr. software to observe the relationships between interior angles and midsegments of triangles. Specific instructions for creating this lesson in Cabri Jr. are...

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#### Ratios in Right Triangles

Learners calculate the sides of right triangles in this trigonometric ratios lesson. They use Cabri Jr. software and TI-83 or TI-84 calculators to find the side lengths and their ratios to each other for various triangles. The provided...

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#### Similar Triangles and Proportions

Pupils investigate similar triangles and proportions as they make conjectures about the length of sides of similar triangles. For this lesson, have your class construct similar triangles using Cabri Jr so that they share a common vertex.

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#### Area Measures and Right Triangles

Your class will investigate the relationship among different triangles. This geometry lesson, demonstrates how to make a connection between triangles and the Pythagorean Theorem. They identify the missing side or angle of a triangle.

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#### Exploring the Circumcenter of a Triangle

Students construct the circumcenter of a triangle. In this constructing the circumcenter of a triangle lesson plan, students construct a triangle using Cabri Jr. Students draw perpendicular bisectors of the sides of the triangle....

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#### Investigating Segments in a Right Triangle

High schoolers explore the concept of right triangles as they construct a right triangle using Cabri Jr. Learners find the midpoint of the hypotenuse and construct a line from the midpoint to the vertex of the right angle. They then...