# Dodecagon

## Dodecagon

Polygon with twelve sides.

• A dodecagon is a regular dodecagon if all its sides are congruent and if all its interior angles are congruent.
• A dodecagon has twelve interior angles; if it is a regular dodecagon, each of its interior angles measures 150°.

### Formula

The formula to calculate the area A of a regular dodecagon of side length c is:

$$\mathit{A}=3c^{2}(2+\sqrt{3})$$

### Examples

• The figure below is a regular dodecagon. The segment a represents its apothem.

• This is an irregular and non-convex dodecagon: