Hendecagon

Regular hendecagon
Edges and vertices	11
Schläfli symbols	{11}
Coxeter–Dynkin diagrams	Image:CDW ring.pngImage:CDW 11.pngImage:CDW dot.png
Symmetry group	Dihedral (D11)
Area (with t=edge length)	Failed to parse (Missing texvc executable; please see math/README to configure.): A = \frac{11}{4}t^2 \cot \frac{\pi}{11} Failed to parse (Missing texvc executable; please see math/README to configure.): \simeq 9.36564 t^2.
Internal angle (degrees)	180*(1-2/11)° =147.2727...°

In geometry, a hendecagon (also undecagon^[1]) is an 11-sided polygon. The name "undecagon" is often seen as incorrect, but the matter is up for debate. The prefix should be the Greek 'hen', not the Latin 'un' (which is also of Greek origin) ^[2]. A hendecagon has 11 sides. A regular hendecagon has internal angles of 147.272727... degrees. The area of a regular hendecagon with side length a is given by

Failed to parse (Missing texvc executable; please see math/README to configure.): A = \frac{11}{4}a^2 \cot \frac{\pi}{11} \simeq 9.36564 a^2.

A regular hendecagon is not constructible with compass and straightedge.

Use in coinage

The Canadian dollar coin, the loonie, is patterned on a regular hendecagonal prism, as is the Indian two-rupee coin.

It was also patterned on the Susan B. Anthony Dollar of the United States from 1979-1981 and again in 1999

See also

• Hendecagram

External links

• Properties of an Undecagon (hendecagon) With interactive animation
• Eric W. Weisstein, Hendecagon at MathWorld.

References

pl:Jedenastokąt foremny

pt:Hendecágono sr:Једанаестоугао