Enneadecagon

Enneadecagon
(OFF file)
Rank	2
Type	Regular
Notation
Coxeter diagram	x19o ()
Schläfli symbol	{19}
Elements
Edges	19
Vertices	19
Vertex figure	Dyad, length 2cos(π/19)
Measures (edge length 1)
Circumradius	${\frac {1}{2\sin {\frac {\pi }{19}}}}\approx 3.03777$
Inradius	${\frac {1}{2\tan {\frac {\pi }{19}}}}\approx 2.99634$
Area	${\frac {19}{4\tan {\frac {\pi }{19}}}}\approx 28.46519$
Angle	${\frac {17\pi }{19}}\approx 161.05263^{\circ }$
Central density	1
Number of external pieces	19
Level of complexity	1
Related polytopes
Army	Enneadecagon
Dual	Enneadecagon
Conjugate	8 total
Abstract & topological properties
Flag count	38
Euler characteristic	0
Orientable	Yes
Properties
Symmetry	I2(19), order 38
Convex	Yes
Nature	Tame

The enneadecagon is a polygon with 19 sides. A regular enneadecagon has equal sides and equal angles.

A circle with radius 3 centered at the center of an enneadecagon of unit edge length intersects its sides. This is related to the fact that $19/3\approx 2\pi$.

Stellations

• 2-enneadecagram
• 3-enneadecagram
• 4-enneadecagram
• 5-enneadecagram
• 6-enneadecagram
• 7-enneadecagram
• 8-enneadecagram
• 9-enneadecagram

External links

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

• Wikipedia contributors. "Enneadecagon".