Hendecagon
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Missing image
11gon.png
11gon.png
A regular hendecagon
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
- <math>A = \frac{11}{4}a^2 \cot \frac{\pi}{11} \simeq 9.36564 a^2.<math>
A regular hendecagon is not constructible with straightedge and compass.
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.