Enneadecagon
An enneadecagon or 19-gon is a shape with 19 sides and 19 corners.[1] It is also known as an enneakaidecagon or a nonadecagon.[2]
| Regular enneadecagon | |
|---|---|
 A regular enneadecagon | |
| Type | Regular polygon |
| Edges and vertices | 19 |
| Schläfli symbol | {19} |
| Coxeter diagram |    |
| Symmetry group | Dihedral (D19), order 2×19 |
| Internal angle (degrees) | ≈161.052° |
| Dual polygon | Self |
| Properties | Convex, cyclic, equilateral, isogonal, isotoxal |
Regular enneadecagon
All sides of a regular enneadecagon are the same length. Each corner is ≈161.052°. All corners added together equal 6840°.
The radius of the circumcircle of the regular enneadecagon with side length t is (angle in degrees). The area, where t is the edge length, is
References
- Borges, Samantha; Morgan, Matthew (2012), Children's Miscellany: Useless Information That's Essential to Know, Chronicle Books, p. 110, ISBN 9781452119731.
- McKinney, Sueanne; Hinton, KaaVonia (2010), Mathematics in the K-8 Classroom and Library, ABC-CLIO, p. 67, ISBN 9781586835224.
Other websites
- Eric W. Weisstein, Enneadecagon at MathWorld.
Special cases, including regular polygons with their own names, in parentheses List of polygons by number of sides | ||
| 1–10 sides |  | |
| 11–20 sides | ||
| 21–30 sides | ||
| 31–40 sides | ||
| 41–50 sides | ||
| 51–100 sides (selected) | ||
| Star polygons (5–12 sides) | ||
| >100 sides | ||
| Triangles | ||
| Quadrilaterals | ||
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