Hendecagon

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A regular hendecagon.

In geometry, a hendecagon is an 11-sided polygon. The same shape is sometimes called an undecagon, but this is incorrect — the prefix should be the Greek 'hen', not the Latin 'un' ^[1]. 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 dollar is also a hendecagon, as is the Indian two-rupee coin.

[edit] See Also

Hendecagram

[edit] External links

Properties of an Undecagon (hendecagon) With interactive animation

[edit] References

1: http://mathworld.wolfram.com/Hendecagon.html

Polygons
Triangle • Quadrilateral • Pentagon •Hexagon • Heptagon • Octagon • Enneagon (Nonagon) • Decagon • Hendecagon • Dodecagon • Triskaidecagon • Pentadecagon • Hexadecagon • Heptadecagon • Enneadecagon • Icosagon • Chiliagon • Myriagon