Great retrosnub icosidodecahedron

From Wikipedia, the free encyclopedia

Great retrosnub icosidodecahedron

Type	Uniform polyhedron
Elements	F=92, E=150, V=60 (χ=2)
Faces by sides	(20+60){3}+12{⁵/₂}
Wythoff symbol	\|³/₂ ⁵/₃ 2
Symmetry group	I
Index references	U₇₄, C₉₀, W₁₁₇
(3⁴.⁵/₂)/2 (Vertex figure)	Great pentagrammic hexecontahedron (dual polyhedron)

In geometry, the great retrosnub icosidodecahedron is a nonconvex uniform polyhedron, indexed as U₇₄.

[edit] Cartesian coordinates

Cartesian coordinates for the vertices of a great retrosnub icosidodecahedron are all the even permutations of

(±2α, ±2, ±2β),

(±(α−βτ−1/τ), ±(α/τ+β−τ), ±(−ατ−β/τ−1)),

(±(ατ−β/τ+1), ±(−α−βτ+1/τ), ±(−α/τ+β+τ)),

(±(ατ−β/τ−1), ±(α+βτ+1/τ), ±(−α/τ+β−τ)) and

(±(α−βτ+1/τ), ±(−α/τ−β−τ), ±(−ατ−β/τ+1)),

with an even number of plus signs, where

α = ξ−1/ξ

and

β = −ξ/τ+1/τ²−1/(ξτ),

where τ = (1+√5)/2 is the golden mean and ξ is the smaller positive real solution to ξ³−2ξ=−1/τ, or approximately 0.3264046. Taking the odd permutations of the above coordinates with an odd number of plus signs gives another form, the enantiomorph of the other one.