Dodecagon
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12gon.png
12gon.png
A regular dodecagon
A dodecagon is 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.
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DodecagonConstructionAni.gif
Dodecagon Construction Animation
DodecagonConstructionAni.gif
Dodecagon Construction Animation
See also
External links
- Dodecagon and Kurschak's Tile and Theorem (http://agutie.homestead.com/files/kurschak1.html) by Antonio Gutierrez from "Geometry Step by Step from the Land of the Incas"
- Dodecagon (http://mathworld.wolfram.com/Dodecagon.html) at MathWorld