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Dodecagon
From Wikipedia, the free encyclopedia
In geometry, a dodecagon is a polygon with exactly twelve sides. When spelled uppercase, the outlines of the letters E and H (and I in a slab 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 dodecagon is given by: 
Alternately, 
where r is the radius of a circumscribed circle.
Contents |
A regular dodecagon is constructible with compass and straightedge. 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.
 Semiregular tiling 3.12.12 |
 Semiregular tiling: 4.6.12 |
 A demiregular tiling: 3.3.4.12 & 3.3.3.3.3.3 |
- The Australian 50-cent coin, Fijian 50-cent, Tongan 50-seniti, and Solomon Island 50-cent coin are 12-sided. Croatian 25 kuna coin has a dodecagonal shape as well. Until July 2005, a Romanian coin (5000 ROL) was also dodecagonal. The Canadian penny was dodecagonal from 1982 to 1996 as well as the South Vietnamese 20 Ðong coin till 1975. Zambian 50 ngwee (till 1992) and Malawian 50 tambala (till 1995) coins were dodecagonal.
- dodecagonal number
- Dodecahedron - a regular polyhedron with 12 pentagonal faces.
- Dodecagon and Kurschak's Tile and Theorem by Antonio Gutierrez from "Geometry Step by Step from the Land of the Incas"
- Eric W. Weisstein, Dodecagon at MathWorld.
- Kürschak's Tile and Theorem
- Definition and properties of a dodecagon With interactive animation
| Polygons |
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| Triangle • Quadrilateral • Pentagon •Hexagon • Heptagon • Octagon • Enneagon (Nonagon) • Decagon • Hendecagon • Dodecagon • Triskaidecagon • Pentadecagon • Hexadecagon • Heptadecagon • Enneadecagon • Icosagon • Chiliagon • Myriagon |