Hendecagon

A hendecagon

A hendecagon or undecagon or 11-gon is a shape with 11 sides and 11 corners.

Regular hendecagon

All sides of a regular hendecagon are the same length. Each corner is 147.27°. All corners added together equal 1619.97°.

Area

The amount of space a regular hendecagon takes up is

$\alpha =\frac{(n-2)}{n}\cdot 180^{\circ }=\frac{9}{11}\cdot 180^{\circ }\approx 147,273^{\circ }$

$A=\frac{11}{4}{a}^2\cot \frac{\pi }{11}\approx 9,36564a^2$

a is the length of one of its sides.