Pentagon

In geometry, a pentagon is any five-sided polygon.

Related Topics:
Geometry - Polygon

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However, the term is commonly used to mean a regular pentagon, where all sides are equal and all angles are equal (to 108°). Its Schläfli symbol is {5}.

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The area of a regular pentagon with side length a is given by

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A = rac{5a^2}{4}cot rac{pi}{5} = rac {a^2}{4} sqrt{25+10sqrt{5}} simeq 1.72048 a^2

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A pentagram can be formed from a regular pentagon either by extending its sides or by drawing its diagonals, and the resulting figure contains various lengths related by the golden ratio, φ = (1+√5)/2.

Related Topics:
Pentagram - Golden ratio

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