Define an exterior angle of a triangle.

An exterior angle is formed when one side of a triangle is extended beyond its vertex.

State the exterior angle theorem.

The measure of an exterior angle of a triangle is equal to the sum of the two non-adjacent interior angles.

The two non-adjacent interior angles

Name: Exterior Angles of Triangles
Author: Insta~Lesson

10th Grade · Math · 45 min

I can apply the exterior angle theorem to solve for unknown angles in triangles.

1
An exterior angle is formed when one side of a triangle is extended beyond its vertex.
2
The exterior angle theorem states that the measure of an exterior angle is equal to the sum of the two non-adjacent interior angles.
3
If ∠ACD is an exterior angle of triangle ABC, then ∠ACD = ∠A + ∠B.

We would love to help you present Insta~Lesson to your colleagues and administrators. Here are a few resources you can use:

A simple one-pager you can use to share Insta~Lesson.

Learn how Insta~Lesson makes life easier for teachers. This is a great resource to share at a staff meeting or PD!

Learn more about Insta~Lesson's dedicated supports for partner schools.