Lesson: Exterior Angles of a Triangle Mathematics • 8th Grade

In this lesson, we will learn how to find the measure of the exterior angle of a triangle and compare between an exterior angle and its corresponding remote interior angles.

Lesson Plan

Students will be able to

know the definition of an exterior angle of a triangle,
know the definition of an interior angle of a triangle,
know that the exterior angles of a triangle sum to ,
solve problems involving exterior and interior angles of triangles.

Lesson Video

Lesson Worksheet

Q1:

The figure shows some angles identified on triangle .

Identify which angle is an exterior angle.

Identify which angle is an interior angle.

Q2:

Is the measure of two right angles less than, equal to or greater than the sum of the interior angles of a triangle?

Q3:

What is the measure of an exterior angle of an equilateral triangle?