Exterior Angles of Polygons

The Exterior Angle is the angle between any side of a shape,
and a line extended from the next side.

Note: when 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

The Exterior Angles of a Polygon add up to 360°

 

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

 

 
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