Octadecagram

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Octadecagram
Rank2
TypeRegular
Notation
Bowers style acronymOdge
Coxeter diagramx18/5o ()
Schläfli symbol{,18/5}
Elements
Edges18
Vertices18
Vertex figureDyad, length 2cos(5π/18)
Measures (edge length 1)
Circumradius
Inradius
Area
Angle80°
Central density5
Number of external pieces36
Level of complexity2
Related polytopes
ArmyOd, edge length
DualOctadecagram
ConjugatesOctadecagon, great octadecagram
Convex coreOctadecagon
Abstract & topological properties
Flag count36
Euler characteristic0
Schläfli type{18}
OrientableYes
Properties
SymmetryI2(18), order 36
ConvexNo
NatureTame

The octadecagram, or odge, is a non-convex polygon with 18 sides. It's created by taking the fourth stellation of an octadecagon. A regular octadecagram has equal sides and equal angles.

It is one of two regular 18-sided star polygons, the other being the great octadecagram.

It is the uniform quasitruncation of the great enneagram.