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In geometry, a locus (plural: ''loci'') is a set of points whose location satisfies or is determined by one or more specified conditions. ==Commonly studied loci== Examples from plane geometry include: * The set of points equidistant from two points is a perpendicular bisector to the line segment connecting the two points.〔George E. Martin, ''The Foundations of Geometry and the Non-Euclidean Plane'', Springer-Verlag, 1975〕 * The set of points equidistant from two lines that cross is the angle bisector. * All conic sections are loci: * * Parabola: the set of points equidistant from a single point (the focus) and a line (the directrix). * * Circle: the set of points for which the distance from a single point is constant (the radius). The set of points for each of which the ratio of the distances to two given foci is a positive constant (that is not 1) is referred to as a Circle of Apollonius. * *Hyperbola: the set of points for each of which the absolute value of the difference between the distances to two given foci is a constant. * *Ellipse: the set of points for each of which the sum of the distances to two given foci is a constant. The circle is the special case in which the two foci coincide with each other. 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「Locus (mathematics)」の詳細全文を読む スポンサード リンク
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