Triangle Teacher Resources

Find Triangle lesson plans and worksheets
Showing 25 - 48 of 6,788 resources
3:08
Lesson Planet

Constructing SSS Triangles

For Students 8th - 11th Standards
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...
3:58
Lesson Planet

Triangle Angle Sum

For Students 9th - 12th Standards
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.
2:22
Lesson Planet

Constructing ASA Triangles

For Students 8th - 11th Standards
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

For Students 4th - 5th Standards
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...
4:49
Lesson Planet

The Mathematical Secrets of Pascal’s Triangle

For Students 7th - 12th Standards
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...
1 In 1 Collection
Lesson Planet

Verifying Triangles are Congruent

For Teachers 9th - 11th Standards
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

For Teachers 7th - 9th Standards
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

For Teachers 3rd - 5th
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

For Students 4th - 7th Standards
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...
2:49
Lesson Planet

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

For Teachers 6th - 10th
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

For Teachers 4th - 6th Standards
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

For Teachers 11th - 12th Standards
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

For Teachers 8th - 10th Standards
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...
1 In 1 Collection
Lesson Planet

Right Triangles Inscribed in Circles II

For Teachers 9th - 10th Standards
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

For Teachers 9th - 10th Standards
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

For Teachers 7th - 8th Standards
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...
7:40
Lesson Planet

Triangles

For Students 4th - 8th Standards
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...
4:55
Lesson Planet

Classifying Triangles: Lesson

For Students 4th - 8th Standards
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.
3:02
Lesson Planet

Equilateral Triangles: Lesson

For Students 8th - 11th Standards
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

For Teachers 8th Standards
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

For Students 9th - 11th Standards
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...
10:53
Lesson Planet

45-45-90 Triangles

For Students 9th - 12th Standards
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

For Students K - 12th Standards
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....
2:41
Lesson Planet

Congruent Triangles: Lesson

For Students 9th - 12th Standards
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...