In geometry, the great truncated icosidodecahedron (or great quasitruncated icosidodecahedron or stellatruncated icosidodecahedron) is a nonconvex uniform polyhedron, indexed as U68.
It has 62 faces (30 squares, 20 hexagons, and 12 decagrams), 180 edges, and 120 vertices.
[1] It is given a Schläfli symbol t0,1,2{5/3,3}, and Coxeter-Dynkin diagram, .
Cartesian coordinates for the vertices of a great truncated icosidodecahedron centered at the origin are all the even permutations of
φ ,
φ ,
1 φ
2 φ ,
1 φ
φ
φ ,
φ
3 φ
{\displaystyle {\begin{array}{ccclc}{\Bigl (}&\pm \,\varphi ,&\pm \,\varphi ,&\pm {\bigl [}3-{\frac {1}{\varphi }}{\bigr ]}&{\Bigr )},\\{\Bigl (}&\pm \,2\varphi ,&\pm \,{\frac {1}{\varphi }},&\pm \,{\frac {1}{\varphi ^{3}}}&{\Bigl )},\\{\Bigl (}&\pm \,\varphi ,&\pm \,{\frac {1}{\varphi ^{2}}},&\pm {\bigl [}1+{\frac {3}{\varphi }}{\bigr ]}&{\Bigr )},\\{\Bigl (}&\pm \,{\sqrt {5}},&\pm \,2,&\pm \,{\frac {\sqrt {5}}{\varphi }}&{\Bigr )},\\{\Bigl (}&\pm \,{\frac {1}{\varphi }},&\pm \,3,&\pm \,{\frac {2}{\varphi }}&{\Bigr )},\end{array}}}
is the golden ratio.
The great disdyakis triacontahedron (or trisdyakis icosahedron) is a nonconvex isohedral polyhedron.
It is the dual of the great truncated icosidodecahedron.
Its faces are triangles.
The triangles have one angle of
arccos
arccos
arccos
The dihedral angle equals
arccos
Part of each triangle lies within the solid, hence is invisible in solid models.
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