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Catalan surface : ウィキペディア英語版 | Catalan surface
In geometry, a Catalan surface, named after the Belgian mathematician Eugène Charles Catalan, is a ruled surface all of whose rulings are parallel to a fixed plane. The vector equation of a Catalan surface is given by :''r'' = ''s''(''u'') + ''v'' ''L''(''u''), where ''r'' = ''s''(''u'') is the space curve and ''L''(''u'') is the unit vector of the ruling at ''u'' = ''u''. All the vectors ''L''(''u'') are parallel to the same plane, called the ''directrix plane'' of the surface. This can be characterized by the condition: the mixed product (''L' ''(''u''), ''L" ''(''u'') ) = 0.() The parametric equations of the Catalan surface are ()
If all the rulings of a Catalan surface intersect a fixed line, then the surface is called a conoid. Catalan proved that the helicoid and the plane were the only ruled minimal surfaces. ==See also==
*Ruled surface *Conoid * generalized helicoid
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「Catalan surface」の詳細全文を読む
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