Tridecagon

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

A regular tridecagon is represented by Schläfli symbol {13}.

Regular tridecagon

The measure of each internal angle of a regular tridecagon 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.

Numismatic use

The regular tridecagon is used as the shape of the Czech 20 korun coin.[1]

Petrie polygons

The regular tridecagon is the Petrie polygon 12-simplex:

References

Colin R. Bruce, II, George Cuhaj, and Thomas Michael, 2007 Standard Catalog of World Coins, Krause Publications, 2006, ISBN 0896894290, p. 81.

External links

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

Mathematics Encyclopedia