Enneadecagon

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Regular enneadecagon
Regular enneadecagon.svg
Edges and vertices 19
Schläfli symbol {19}
Coxeter–Dynkin diagram CDW ring.pngCDW 19.pngCDW dot.png
Symmetry group Dihedral (D19)
Area
(with t=edge length)		 \frac{19}{4}t^2 \cot \frac{\pi}{19}
\simeq 28.4652\,t^2.
Internal angle
(degrees)		 ~161.052°
Properties convex, cyclic, equilateral, isogonal, isotoxal

In geometry, an enneadecagon is a polygon with 19 sides and angles. It is also known as an enneakaidecagon or a nonadecagon.

The radius of the circumcircle of the regular enneadecagon with side length t is

R=\frac{t}{2} \csc \frac {180}{19} (angle in degrees)

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Polygons
Listed by number of sides
1–10 sides
11–20 sides
Hendecagon · Dodecagon · Triskaidecagon · Tetradecagon · Pentadecagon · Hexadecagon · Heptadecagon · Octadecagon · Nonadecagon (Enneadecagon) · Icosagon
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