What are Interior and Exterior Angles of a Polygon?

Interior angles are the angles located on the INSIDE of a polygon
Exterior angles are the angles that are formed OUTSIDE the polygon when the sides are extended
Interior and exterior angles that are adjacent to each other are supplementary, or add up to 180°
The exterior angles of ANY polygon always add up to 360°

1. "Interior" means "inside"
1. "Interior" means "inside"
2. Polygons will have as many interior angles as they do sides
3. So since our polygon has 5 sides, it has 5 interior angles
1. "Exterior" means "outside"
1. "Exterior" means "outside"
2. When the sides of a polygon are extended out, new angles are created adjacent to the interior angles
3. These new angles are the exterior angles
1. Interior angles and exterior angles that are next to each other form straight lines
1. Supplementary angles add up to 180°
2. Since each interior and exterior angle pair forms a straight line, if you add them together you'll get 180°
3. So if you were trying to find a missing exterior angle, you could just subtract its corresponding interior angle from 180 to get its measure
4. And it works the other way around as well
1. This is true for ANY polygon, no matter how many sides it has

Definition: Interior and exterior angles