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An octagon is a polygon that has eight sides. The internal angle at each vertex of a regular octagon is 135°. The area of a regular octagon of side length a is given by
- <math>A = 2a^2 \cot \frac{\pi}{8} = 2(1+\sqrt{2})a^2 \simeq 4.82843 a^2.<math>
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Concave_octagon.png
Concave Octagon
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Complex_octagon.png
Complex Octagon
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| regular | irregular | concave | complex
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Worldwide, stop signs are regular octagons.
See also
In architecture, an octagon house is a house built in an octagonal shape. Monticello is the most famous example.
In mixed martial arts, The Octagon is the name of the octagonal ring used in the Ultimate Fighting Championship, and by metonymy a term for the UFC itself as well.
The Octagon is the name of the city centres of Bristol, England, and Dunedin, New Zealand.
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