Sum of the Interior Angle Measures of a Polygon

What is the sum of a polygon's interior angle measures?

Professor Kellie Evans (kellie.m.evans@csun.edu)

Warm-up activity: Angle sum of a triangle.

Load GeoGebra activity

What is the interior angle sum of a regular n-gon?

What about the angle sum for n-gons that aren't regular?
What if the n-gon is concave? Does the answer change?