Dodecagon

A dodecagon isoppoo a polygon with exactly twelve sides. When spelled uppercase, the outlines of the letters E and H (and I in a serif font) are all dodecagons.

A regular dodecagon is a dodecagon with all sides having equal length and all interior angles having the same size of 150 degrees. The area of a regular decagon is given by

<math>A = 3 a^2 \cot \frac{\pi}{12} = 3 a^2 \left( 2+\sqrt{3} \right) \simeq 11.1962 a^2.<math>

Dodecagon construction

A regular dodecagon is constructible with straightedge and compass. The following is a 23 step animation illustrating one way it can be done. Notice that the compass radius is unaltered during steps 8 through 11.

See also

• geometry
• dodecagonal number

External links

• Dodecagon and Kurschak's Tile and Theorem by Antonio Gutierrez from "Geometry Step by Step from the Land of the Incas"
• Dodecagon at MathWorld