Geometry · Quadrilaterals & Polygons
Interior Angle Sum
HSG-CO.C.11
Definition
The total of a polygon's interior angles, equal to (n - 2) times 180 degrees.
Examples
- A pentagon (5 sides): (5 - 2) x 180 = 540 degrees.
- A hexagon (6 sides): (6 - 2) x 180 = 720 degrees.
Key rule
The interior angle sum depends only on the number of sides, n.
Memory hook
(n - 2) x 180 degrees — subtract 2, multiply by 180.