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A chord of a circle is a straight line segment whose endpoints both lie on the circle. A secant line, or just ''secant'', is the infinite line extension of a chord. More generally, a chord is a line segment joining two points on any curve, for instance an ellipse. A chord that passes through a circle's center point is the circle's diameter. == Chords of a circle == Among properties of chords of a circle are the following: # Chords are equidistant from the center only if their lengths are equal. # A chord that passes through the center of a circle is called a diameter, and is the longest chord. # If the line extensions (secant lines) of chords AB and CD intersect at a point P, then their lengths satisfy AP·PB = CP·PD (power of a point theorem). The area that a circular chord "cuts off" is called a circular segment. Chord is from the Latin ''chorda'' meaning ''bowstring''. 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「Chord (geometry)」の詳細全文を読む スポンサード リンク
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