# Exterior Angles of Polygons

### The Exterior Angle is the angle between any side of a shape,

and a line extended from the next side.

Another example:

When we add up the Interior Angle and Exterior Angle we get a straight line 180°. They are "Supplementary Angles".

## Polygons

A Polygon is any flat shape with straight sides

The Exterior Angles of a Polygon add up to 360°

images/exterior-angles.js

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

Press Play button to see.

*(Exercise: try this with a square, then with some interesting polygon you invent yourself.)*

Note: This rule only works for simple polygons.

We can also think "each line **changes direction**

until we get back to the start again":

830,831, 1776,832, 1777, 3317, 3318, 3319, 7491, 9062