Octadecagon

Octadecagon
(OFF file)
Rank	2
Type	Regular
Space	Spherical
Notation
Coxeter diagram	x18o
Schläfli symbol	{18}
Elements
Edges	18
Vertices	18
Vertex figure	Dyad, length 2cos(π/18)
Measures (edge length 1)
Circumradius	$\frac{1}{2\sin\frac{\pi}{18}} ≈ 2.87939$
Inradius	$\frac{1}{2\tan\frac{\pi}{18}} ≈ 2.83564$
Area	$\frac{9}{2\tan\frac{\pi}{18}} ≈ 25.52077$
Angle	160°
Central density	1
Number of pieces	18
Level of complexity	1
Related polytopes
Army	{18}
Dual	Octadecagon
Conjugates	Octadecagram, great octadecagram
Abstract properties
Euler characteristic	0
Topological properties
Orientable	Yes
Properties
Symmetry	I2(18), order 36
Convex	Yes
Nature	Tame

The octadecagon is a polygon with 18 sides. A regular octadecagon has equal sides and equal angles.

Stellations

• 2-octadecagram (compound of 2 enneagons)
• 3-octadecagram (compound of 3 hexagons)
• 4-octadecagram (compound of 2 enneagrams)
• 5-octadecagram
• 6-octadecagram (compound of 6 triangles)
• 7-octadecagram
• 8-octadecagram (compound of 2 great enneagrams)

External links

• Bowers, Jonathan. "Regular Polygons and Other Two Dimensional Shapes".

• Wikipedia Contributors. "Octadecagon".