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In geometry an equilateral pentagon is a polygon with five sides of equal length. Its five internal angles, in turn, can take a range of sets of values, thus permitting it to form a family of pentagons. In contrast, the regular pentagon is unique, because it is equilateral and moreover it is equiangular (its five angles are equal). Four intersecting equal circles arranged in a closed chain are sufficient to determine a convex equilateral pentagon. Each circle's center is one of four vertices of the pentagon. The remaining vertex is determined by one of the intersection points of the first and the last circle of the chain. It is possible to describe any convex equilateral pentagon with only two angles α and β with α ≥ β provided the fourth angle (δ) is the smallest of the rest of the angles. Thus the general equilateral pentagon can be regarded as a bivariate function ''f(α, β)'' where the rest of the angles can be obtained by using trigonometric relations. The equilateral pentagon described in this manner will be unique up to a rotation in the plane. == Examples== Equiangular_pentagon_03.svg|Regular pentagon File:Pentagram green.svg|Regular star pentagram 5-gon equilateral 01.svg|Convex Equilateral_pentagon-30-90.png|Adjacent right angles 5-gon equilateral 03.svg|Concave 5-gon equilateral 05.svg|Degenerate (edge-vertex overlap) Triangle.Isosceles.svg|Degenerate into triangle (colinear edges) File:Polyiamond-3-1.svg|Degenerate into trapezoid (colinear edges) 5-gon equilateral 06.svg|Self-intersecting 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Equilateral pentagon」の詳細全文を読む スポンサード リンク
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