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 1620°.

The amount of space a regular hendecagon takes up is

α = \frac{(n - 2)}{n} \cdot 18 0^{\circ} = \frac{9}{11} \cdot 18 0^{\circ} \approx 147,27 3^{\circ}

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

a is the length of one of its sides.

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v t e Polygons
Special cases, including regular polygons with their own names, in parentheses List of polygons by number of sides
1–10 sides	Henagon Digon Triangle Quadrilateral Pentagon Hexagon Heptagon Octagon Nonagon Decagon
11–20 sides	Hendecagon Dodecagon Tridecagon Tetradecagon Pentadecagon Hexadecagon Heptadecagon Octadecagon Enneadecagon Icosagon
21–100 sides (selected)	Icosikaitetragon (24) Triacontagon (30) Triacontadigon (32) Tetracontagon (40) Pentacontagon (50) Hexacontagon (60) Heptacontagon (70) Octacontagon (80) Enneacontagon (90) Hectogon (100)
>100 sides	257-gon Chiliagon (1,000) Myriagon (10,000) 65537-gon Apeirogon (∞) Circle
Star polygons (5–12 sides)	Pentagram Hexagram Heptagram Octagram Enneagram Decagram Hendecagram Dodecagram
Triangles	Equilateral triangle Isosceles triangle Scalene triangle Right triangle Acute and obtuse triangles
Quadrilaterals	Square Rectangle Rhombus Parallelogram Trapezoid Kite Antiparallelogram