In geometry, a tridecagon (or triskaidecagon) is a polygon with 13 sides and angles. ==Regular tridecagon== ===Numismatic use=== The regular tridecagon is used as the shape of the Czech 20 korun coin. ==Related polygons== A tridecagram is a 13-sided star polygon. There are 5 regular forms given by Schläfli symbols: {13/2}, {13/3}, {13/4}, {13/5},...
A tridecagon is a thirteen-sided polygon.
A 13 sided polygon. See also: Polygon.