# Polygon's interior and exterior angle

A polygon always has an exterior angle sum to 360 no matter the number of sides or their width.

A triangle has an exterior angle sum equal to 360

A square has an exterior angle sum equal to 360

A pentagon has an exterior angle sum equal to 360

Quadrilaterals have exterior angle sum equal to 360

There's a pattern.

All of the above shapes are polygons, and polygons could have n-sides or n-angles.

To find the sum of interior angles for these polygons, we just subtract the exterior angle sum from the interior

```
a + b + ... aN = N * 180 - 360
where a, b .. N are interior angles.
N is number of angles in the polygon.
```