# Tridecagram

Tridecagram
Rank2
TypeRegular
Notation
Coxeter diagramx13/3o ()
Schläfli symbol{13/3}
Elements
Edges13
Vertices13
Measures (edge length 1)
Circumradius${\displaystyle {\frac {1}{2\sin {\frac {3\pi }{13}}}}\approx 0.75401}$
Inradius${\displaystyle {\frac {1}{2\tan {\frac {3\pi }{13}}}}\approx 0.56438}$
Area${\displaystyle {\frac {13}{4\tan {\frac {3\pi }{13}}}}\approx 3.66849}$
Angle${\displaystyle {\frac {7\pi }{13}}\approx 96.92308^{\circ }}$
Central density3
Number of external pieces26
Level of complexity2
Related polytopes
ArmyTad, edge length ${\displaystyle {\frac {\sin {\frac {\pi }{13}}}{\sin {\frac {3\pi }{13}}}}}$
DualTridecagram
ConjugatesTridecagon, Small tridecagram, Medial tridecagram, Great tridecagram, Grand tridecagram
Convex coreTridecagon
Abstract & topological properties
Flag count26
Euler characteristic0
Schläfli type{13}
OrientableYes
Properties
SymmetryI2(13), order 26
Flag orbits1
ConvexNo
NatureTame

The tridecagram is a non-convex polygon with 13 sides. It is the second stellation of a tridecagon. A regular tridecagram has equal sides and equal angles.

It is one of five regular 13-sided star polygons, the other four being the small tridecagram, the medial tridecagram, the great tridecagram, and the grand tridecagram.