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.
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- This is an irregular and non-convex dodecagon:
