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Maths Exercices

Exterior Angles of a Polygon

In a polygon, an exterior angle is formed by a side and an extension of an adjacent side.


The sum of the exterior angles of any polygon is 360º

The measure the one exterior angle of an equangular polygon can be calculated by using the following table:

Number of sides
Measure of 1 exterior angle
Sum of exterior angles
3
120º
3·120º=360º
4
90º
4·90º=360ª
5
72º
5·72º=360º
...
...
...
n
360º/n
360º

What is the degree measure of an exterior angle of a regular nonagon?
A nonagon has nine vertices, so divide the measure of the sum of the exterior angles by 9.

360º ÷ 9 = 40º
The degree measure of an exterior angle of a regular nonagon is 40º