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In the geometry of curves, an orthoptic is the set of points for which two tangents of a given curve meet at a right angle. ; Examples: The orthoptic of :1) a parabola is its directrix (proof: s. parabola), :2) an ellipse is the director circle (s. below), :3) a hyperbola is the circle (in case of there are no orthogonal tangents, s. below), :4) an astroid is a quadrifolium with the polar equation :: can be considered as the orthoptic of two circles which are degenerated to the two points . ''Remark:'' In ''medicine'' there exists the term orthoptic, too. == Orthoptic of an ellipse and hyperbola == 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「Orthoptic (geometry)」の詳細全文を読む スポンサード リンク
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