Triangle Teacher Resources

Find Triangle lesson plans and worksheets
Showing 49 - 72 of 6,788 resources
5:25
Lesson Planet

Comparing Triangle Angles and Sides: Lesson

For Students 7th - 11th
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...
5:21
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Triangle Inequality Theorem: Lesson

For Students 6th - 12th Standards
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...
3:12
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Area and Perimeter of Triangles: Lesson

For Students 6th - 10th Standards
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...
2:28
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Triangle Sum Theorem: Lesson

For Students 6th - 10th Standards
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.
3:01
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Isosceles Triangles: Lesson

For Students 8th - 11th Standards
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.
3:19
Lesson Planet

SAS Triangle Congruence: Lesson

For Students 8th - 11th Standards
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...
3:44
Lesson Planet

Special Right Triangle 45-45-90: Lesson

For Students 8th - 11th
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...
3:17
Lesson Planet

Triangle Proportionality: Lesson

For Students 7th - 11th Standards
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.
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Similar Triangles

For Students 8th Standards
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. 
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Pythagorean Theorem for Solving Right Triangles: Solving the Triangle

For Students 9th - 12th Standards
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...
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Classify Triangles - Homework 15.3

For Students 4th - 6th Standards
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.
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Finding the Area of an Equilateral Triangle

For Teachers 9th - 11th Standards
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...
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Toothpick Triangles

For Teachers 4th - 8th
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...
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Identifying a Triangle by its Sides and Angles

For Teachers 9th - 12th Standards
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,...
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Triangle Sum Theorem

For Teachers 8th - 10th Standards
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...
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Triangles

For Students 4th - 7th Standards
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...
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Best Triangle

For Teachers 9th - 12th Standards
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...
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Exploring Triangle Proportions

For Teachers 7th - 9th
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...
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Triangle Designs - Enrichment 16.5

For Students 4th - 6th
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.
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Slope/Triangle Area Exploration

For Teachers 8th - 11th
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...
3:25
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Draw Triangles Using Given Angles

For Students 6th - 8th Standards
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. 
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The Pythagorean Theorem and Classifying Triangles

For Teachers 9th - 12th Standards
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).
3:50
Lesson Planet

Area of a Triangle

For Students 6th - 8th Standards
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...
9:09
Lesson Planet

Congruent Triangles

For Students 6th - 12th Standards
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...