5.1: Interior & Exterior Angles
This activity is intended to supplement Geometry, Chapter 4, Lesson 1.
Problem 1 – Interior angles of a triangle
1. Record the measures of the interior angles of your triangle.




2. What is the sum of the measures of the three interior angles of the triangle?
3. Does this result change when a vertex of the triangle is dragged?
Problem 2 – One exterior angle of a triangle
4. Record the measures of the interior angles and exterior angle





5. Make some observations about the exterior angle
Problem 3 – Three exterior angles of a triangle
6. List the measures of the exterior angles of your triangle (one at each vertex).
Ext 
Ext 
Ext 

7. Calculate the sum of the three exterior angles.
8. Why do you think it is important to use one exterior angle at each vertex?
Additional Problems
Find the missing angle measures in each of the diagrams below.