Enneadecagon

Regular enneadecagon
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

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

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 $R={\frac {t}{2}}\csc {\frac {180}{19}}$ (angle in degrees). The area, where t is the edge length, is ${\frac {19}{4}}t^{2}\cot {\frac {\pi }{19}}\simeq 28.4652\,t^{2}.$

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.

enneadecagon

Other websites

Eric W. Weisstein, Enneadecagon at MathWorld.

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[1] Borges, Samantha; Morgan, Matthew (2012), Children's Miscellany: Useless Information That's Essential to Know, Chronicle Books, p. 110, ISBN 9781452119731.

[2] McKinney, Sueanne; Hinton, KaaVonia (2010), Mathematics in the K-8 Classroom and Library, ABC-CLIO, p. 67, ISBN 9781586835224.

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