# Triangle Teacher Resources

Find Triangle lesson plans and worksheets
Showing 49 - 72 of 6,721 resources
9:34
Lesson Planet

#### Similar Triangles

For Students 9th - 10th
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...
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...
1:46
Lesson Planet

#### Telly Plays The Triangle

For Teachers Pre-K - K
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,...
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...
5:58
Lesson Planet

#### What is a Triangle?

For Teachers 1st - 5th
Triangles, triangles, triangles. What makes a polygon a triangle? How many types of triangles are there? How do you determine what kind of triangle it is? Watch this video as the teacher explains 'tri' meaning three, making a triangle -...
2 In 2 Collections
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....
5:02
Lesson Planet

#### Why Are the Angles of Equilateral Triangles Always Equal to 60¼?

For Teachers 6th - 10th
Learn how to identify an equilateral triangle by evaluating its congruent sides. Once you've determined that that sides are congruent you'll be able to use the triangle sum theorem to determine the angles in an equilateral triangle. This...
2:12
Lesson Planet

#### What are the Legs and Hypotenuse of a Right Triangle?

For Teachers 6th - 10th
What are all the parts of a right triangle called? What makes it a right triangle? Legs? Triangles have legs? Hypotenuse? Pythagorean Theorem? The instructor diagrams and identifies all the parts of a right triangle for you.
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...
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...
5:09
Lesson Planet

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

For Teachers 8th - 10th
Are you working on finding the missing angles of 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...
2:47
Lesson Planet

#### How Do You Find the Sine of an Angle in a Right Triangle?

For Teachers 7th - 11th
A trigonometric ratio is a ratio between two sides of a right triangle. In this problem, find sin(A) in the given right triangle. Use the ratio of the opposite side over the hypotenuse.
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...
1 In 1 Collection
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...
1 In 1 Collection 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...
5:20
Lesson Planet

#### What is the Formula for the Area of a Triangle?

For Teachers 6th - 12th
The teacher explains how the formula for a triangle was determined. It is related to a parallelogram. What? The formula for the area of a triangle is derived from the area of a parallelogram? Seeing is believing, so watch this video to...
5:44
Lesson Planet

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

For Teachers 6th - 12th
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

#### Amazing Triangles

For Teachers 3rd - 6th
Student scientists investigate triangle structures. In this building lesson plan, students explore how to design triangle braces in the construction of structures in order to build a stronger base.
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...
5:07
Lesson Planet

#### How Do You Find a Missing Side of a Right Triangle Using Cosine?

For Teachers 6th - 11th
Trigonometry? What's trigonometry. Well, something to do with triangles, right? Right! Right triangles! In this problem, find the missing length of one of the sides. So set this up as a ratio: cosine(A) = adjacent side length divided by...
Lesson Planet

#### Triangles

For Teachers 4th - 5th
If you're about to begin a unit on the different types of triangles, this would be a good presentation for you to employ.Viewers are exposed to the three main types of triangles: congruent, isosceles, and equilateral. They are coached on...