Geometry · JSS 1
Interior angles of a polygon
Find the total, or each, interior angle of a shape with n sides.
- Sum of interior angles = (n − 2) × 180°
- Each angle of a regular polygon = (n − 2) × 180°n
What the letters mean
- n
- the number of sides
Worked example
Find each interior angle of a regular hexagon.
Step 1: A hexagon has 6 sides
Sum = (6 − 2) × 180° = 720°
Step 2: Share equally
720° ÷ 6 = 120°
Final answer: 120°
See it
Play with this picture from the Plane Shapes lesson.
Rectangle · a quadrilateral
- Sides
- 4
- Right angles
- 4
- Parallel pairs
- 2
- Lines of symmetry
- 2
- Regular?
- No
- Angle sum
- 360°
- (4 − 2) × 180° = 360°
Tick marks show equal sides; arrows show parallel sides.