Interior angle sum of a polygon

Overview

Split from one vertex into triangles to see (n − 2)×180°.

Explanation

For an n-gon (n ≥ 3), interior angle sum = (n − 2)×180°.
Proof: diagonals from one vertex make n − 2 triangles.
Each interior angle of a regular n-gon is (n − 2)×180°/n.

How to use

Change n and watch diagonals carve n − 2 triangles.

Knowledge points

• Polygons
• Angle sum