Great truncated icosidodecahedron

Template:Short description Template:Uniform polyhedra db File:Great truncated icosidodecahedron.stl 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. It is given a Schläfli symbol Template:Math and Coxeter-Dynkin diagram, Template:CDD.

Cartesian coordinates

Cartesian coordinates for the vertices of a great truncated icosidodecahedron centered at the origin are all the even permutations of $$\begin{array}{ccccc}(& \pm \phi ,& \pm \phi ,& \pm [3-\frac{1}{\phi }]& ),\\ (& \pm 2\phi ,& \pm \frac{1}{\phi },& \pm \frac{1}{{\phi }^3}& ),\\ (& \pm \phi ,& \pm \frac{1}{{\phi }^2},& \pm [1+\frac{3}{\phi }]& ),\\ (& \pm \sqrt{5},& \pm 2,& \pm \frac{\sqrt{5}}{\phi }& ),\\ (& \pm \frac{1}{\phi },& \pm 3,& \pm \frac{2}{\phi }& ),\end{array}$$

where $\phi =\frac{1+\sqrt{5}}{2}$ is the golden ratio.

Related polyhedra

Great disdyakis triacontahedron

Template:Uniform polyhedra db File:Great disdyakis triacontahedron.stl 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.

Proportions

The triangles have one angle of $\arccos (\frac{1}{6}+\frac{1}{15}\sqrt{5})\approx 71.59463622088^{\circ }$, one of $\arccos (\frac{3}{4}+\frac{1}{10}\sqrt{5})\approx 13.19299904074^{\circ }$ and one of $\arccos (\frac{3}{8}-\frac{5}{24}\sqrt{5})\approx 95.21236473838^{\circ }.$ The dihedral angle equals $\arccos \left(\frac{-179+24\sqrt{5}}{241}\right)\approx 121.33625080739^{\circ }.$ Part of each triangle lies within the solid, hence is invisible in solid models.

See also

• List of uniform polyhedra

References

• Template:Citation p. 96

External links

• Template:Mathworld
• Template:Mathworld

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