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In mathematics, a crunode (archaic) or node is a point where a curve intersects itself so that both branches of the curve have distinct tangent lines at the point of intersection. A crunode is also known as an ''ordinary double point''. For a plane curve, defined as the locus of points ''f''(''x'', ''y'') = 0, where ''f''(''x'', ''y'') is a smooth function of variables ''x'' and ''y'' ranging over the real numbers, a crunode of the curve is a singularity of the function ''f'', where both partial derivatives and vanish. Further the Hessian matrix of second derivatives will have both positive and negative eigenvalues. ==See also== *Singular point of a curve *Acnode *Cusp *Tacnode *Saddle point 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「Crunode」の詳細全文を読む スポンサード リンク
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