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In geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90-degree angles, or right angles).〔(Weisstein, Eric W. "Square." From MathWorld--A Wolfram Web Resource. )〕 It can also be defined as a rectangle in which two adjacent sides have equal length. A square with vertices ''ABCD'' would be denoted . The square is the n=2 case of the families of n-hypercubes and n-orthoplexes. A square has Schläfli symbol . A truncated square, t, is an octagon, . An alternated square, h, is a digon, . ==Characterizations== A convex quadrilateral is a square if and only if it is any one of the following:〔Zalman Usiskin and Jennifer Griffin, "The Classification of Quadrilaterals. A Study of Definition", Information Age Publishing, 2008, p. 59, ISBN 1-59311-695-0.〕〔(J. Wilson, ''Problem set 1.3'', 2010 )〕 * a rectangle with two adjacent equal sides * a quadrilateral with four equal sides and four right angles * a parallelogram with one right angle and two adjacent equal sides * a rhombus with a right angle * a rhombus with all angles equal * a quadrilateral where the diagonals are equal and are the perpendicular bisectors of each other, i.e. a rhombus with equal diagonals 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「Square」の詳細全文を読む スポンサード リンク
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