Hendecagon

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A regular hendecagon.

In geometry, a hendecagon is an 11-sided polygon. Undecagon is incorrect — the prefix is properly Greek, not Latin. A regular hendecagon has internal angles of 147.272727... degrees. The area of a regular hendecagon with side length a is given by

$A = \frac{11}{4}a^2 \cot \frac{\pi}{11} \simeq 9.36564 a^2.$

A regular hendecagon is not constructible with compass and straightedge.

The Canadian dollar coin, the Loonie, is a hendecagon. The interior design of the (US coin) Susan B. Anthony silver dollar is also a hendecagon. The Indian two-rupee coin is also a hendecagon.

[edit] External links

Properties of an Undecagon (hendecagon) With interactive animation

Polygons
Triangle \| Quadrilateral \| Pentagon \| Hexagon \| Heptagon \| Octagon \| Enneagon (Nonagon) \| Decagon \| Hendecagon \| Dodecagon \| Triskaidecagon \| Pentadecagon \| Hexadecagon \| Heptadecagon \| Enneadecagon \| Icosagon \| Icosihenagon \| Tricontagon \| Pentacontagon \| Hectagon \| Chiliagon \| Myriagon