Write a proof of the Polygon Interior Angle-Sum Theorem.
The sum of the measures of the interior angles of a convex n-gon is 180 times (n-2).
By drawing every diagonal from one vertex in a convex, n-sided polygon, the polygon can be decomposed into how many triangles?
You can always decompose a polygon into n-2 triangles, of which each is a triangle. The sum of the angles in a triangle is 180, so you get the formula 180(n-2).
The n-sided polygon can always be decomposed into n-2 triangles.
