Exterior Angles of Polygons

Note: If you add up the Interior Angle and Exterior Angle you get a straight line, 180°. (See Supplementary Angles)

Polygons

A Polygon is any flat shape with straight sides

In other words the exterior angles add up to one full revolution

Think of it this way: the lines change direction and eventually return back to the start.

(Exercise: try this with a square or some odd-shaped polygon)

Note: This rule only works for simple polygons