Tridecagon

Regular tridecagon
A regular tridecagon
Type	Regular polygon
Edges and vertices	13
Schläfli symbol	{13}
Coxeter diagram
Symmetry group	Dihedral (D13), order 2×13
Internal angle (degrees)	≈152.308°
Dual polygon	Self
Properties	Convex, cyclic, equilateral, isogonal, isotoxal

A tridecagon or trikaidecagon or triskaidecagon or trisdecagon or 13-gon is a shape with 13 sides and 13 corners.

Regular tridecagon

All sides of a regular tridecagon are the same length. Each corner is 147.27°. All corners added together equal 6840°.

Area

The amount of space a regular tridecagon takes up is

$A={\frac {13}{4}}a^{2}\cot {\frac {\pi }{13}}\simeq 13.1858\,a^{2}.$

a is the length of one of its sides.

Numismatic use

The regular tridecagon is used as the shape of the Czech 20 korun coin.

Other pages

• Triskaidekaphobia

Other websites

• Eric W. Weisstein, Tridecagon at MathWorld.