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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Rhombic triacontahedron ： ウィキペディア英語版 Rhombic triacontahedron In geometry, the rhombic triacontahedron, sometimes simply called the triacontahedron as it is the most common thirty-faced polyhedron, is a convex polyhedron with 30 rhombic faces. It has 60 edges and 32 vertices of two types. It is a Catalan solid, and the dual polyhedron of the icosidodecahedron. It is a zonohedron. The ratio of the long diagonal to the short diagonal of each face is exactly equal to the golden ratio, ''φ'', so that the acute angles on each face measure , or approximately 63.43°. A rhombus so obtained is called a ''golden rhombus''. Being the dual of an Archimedean solid, the rhombic triacontahedron is ''face-transitive'', meaning the symmetry group of the solid acts transitively on the set of faces. This means that for any two faces, A and B, there is a rotation or reflection of the solid that leaves it occupying the same region of space while moving face A to face B. The rhombic triacontahedron is somewhat special in being one of the nine edge-transitive convex polyhedra, the others being the five Platonic solids, the cuboctahedron, the icosidodecahedron, and the rhombic dodecahedron. The rhombic triacontahedron is also interesting in that its vertices include the arrangement of four Platonic solids. It contains ten tetrahedra, five cubes, an icosahedron and a dodecahedron. ==Dimensions== If the edge length of a rhombic triacontahedron is ''a'', surface area, volume, the radius of an inscribed sphere (tangent to each of the rhombic triacontahedron's faces) and midradius, which touches the middle of each edge are:〔Stephen Wolfram, "()" from Wolfram Alpha. Retrieved January 7, 2013.〕 $S\; =\; a^2\; \backslash cdot\; 12\backslash sqrt\; \backslash approx\; 26.8328\; \backslash cdot\; a^2$ $V\; =\; a^3\; \backslash cdot\; 4\backslash sqrt\; \backslash approx\; 1.37638\; \backslash cdot\; a$ $r\_m\; =\; a\; \backslash cdot\; \backslash left(1+\backslash frac\{\backslash sqrt5\{\}\}\backslash right)\; \backslash approx\; 1.44721\; \backslash cdot\; a$ where ''φ'' is the golden ratio. The plane of each face is perpendicular to the center of the rhombic triacontahedron, and is located at the same distance (short diagonals belong only to the edges of the inscribed regular dodecahedron, while long diagonals are included only in edges of the inscribed icosahedron). Using one of the three orthogonal golden rectangles drawn into the inscribed icosahedron we can easily deduce the distance between the center of the solid and the center of its rhombic face. 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「Rhombic triacontahedron」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.