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In geometry, polyhedra are associated into pairs called ''duals'', where the vertices of one correspond to the faces of the other. Starting with any given polyhedron, the dual of its dual is the original polyhedron. The dual of an isogonal polyhedron, having equivalent vertices, is one which is isohedral, having equivalent faces, and of one which is isotoxal, having equivalent edges, is also isotoxal. The regular polyhedra — the Platonic solids and Kepler-Poinsot polyhedra — form dual pairs, with the exception of the regular tetrahedron which is self-dual. Duality is closely related to ''reciprocity'' or ''polarity''. ==Kinds of duality== There are many kinds of duality. The kinds most relevant to elementary polyhedra are: *Polar reciprocity *Topological or abstract duality 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「Dual polyhedron」の詳細全文を読む スポンサード リンク
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