Nonagon

Dalam geometri, nonagon (atau enneagon) ialah poligon sembilan sisi.

Nonagon biasa mempunyai sudut dalaman 140°. Luas kawasan nonagon biasa yang panjang sisinya a ialah diberi

$A={\frac {9}{4}}a^{2}\cot {\frac {\pi }{9}}\simeq 6.18182\,a^{2}.$

Graphs and stars

The K₉ complete graph is often drawn as a regular nonagon with all 36 edges connected. This graph also represents an orthographic projection of the 9 vertices and 36 edges of the 8-simplex.

The regular nonagon also contains 3 star figures, the third being the compound of three equilateral triangles:

Pop culture references

They Might Be Giants have a song entitled "Nonagon" on their children's album "Here Come the 123s." It refers to both an attendee at a party at which "everybody in the party is a many-sided polygon" and a dance they perform at this party.[1]

References

• Eric W. Weisstein, Nonagon di MathWorld.

External links

• Properties of a Nonagon (with interactive animation)