Tridecagon

Regular triskaidecagon
Edges and vertices	13
Schläfli symbol	{13}
Coxeter–Dynkin diagram
Symmetry group	Dihedral (D13)
Area (with t=edge length)	${\frac {13}{4}}t^{2}\cot {\frac {\pi }{13}}$ $\simeq 13.1858\,t^{2}$
Internal angle (degrees)	180*(11/13) degrees $\simeq 152.308$

In geometry, a triskaidecagon (or tridecagon) is a polygon with 13 sides and angles.

The measure of each internal angle of a regular triskaidecagon is approximately 152.308 degrees, and the area with side length a is given by

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

A regular triskaidecagon is not constructible with compass and straightedge. However, it is constructible using a Neusis construction.

Related polygons

A triskaidecagram is a 13-sided star polygon. There are 5 regular forms given by Schläfli symbols: {13/2}, {13/3}, {13/4}, {13/5}, {13/6}.

External links

• Weisstein, Eric W. "Tridecagon". MathWorld.