Angles of Polygons

A 3-sided polygon is called a TRIANGLE

A 4-sided polygon is called a QUADRILATERAL

A 5-sided polygon is called a PENTAGON

A 6-sided polygon is called a HEXAGON

A 8-sided polygon is called a OCTAGON

A 9-sided polygon is called a NONAGON

A 10-sided polygon is called a DECAGON

To find the interior angle sum of a polygon, we follow two easy steps.

First, take the number of sides and subtract two. In our formula this will appear as $\left(n-2\right)$   with n being the number of sides.

Second, multiply by 180.

 $Interior\ Sum\ =\ 180\left(n-2\right)$  

If we want to find the measure of ONE angle in a shape instead of the sum, we use this formula: $\frac{Sum}{Sides}$   

First find the sum of the interior angles, then divide by the number of sides.