Gyroelongated pentagonal rotunda

Gyroelongated pentagonal rotunda
(3D model) (OFF file)
Rank	3
Type	CRF
Space	Spherical
Notation
Bowers style acronym	Gyepro
Elements
Faces	5+5+5+5+10 triangles, 1+5 pentagons, 1 decagon
Edges	5+5+5+10+10+10+10+10
Vertices	5+5+5+5+10
Vertex figures	10 rectangles, edge lengths 1 and (1+√5)/2
	10 irregular pentagons, edge lengths 1, 1, 1, 1, (1+√5)/2
	10 Isosceles trapezoids, edge lengths 1, 1, 1, √(5+√5)/2
Measures (edge length 1)
Volume	$\frac{45+17\sqrt5+10\sqrt{2-2\sqrt5+2\sqrt{650+290\sqrt5}}}{12} ≈ 13.66705$
Dihedral angles	3–3 join: $\arccos\left(\sqrt{\frac{5-2\sqrt5}{15}}\right)+\arccos\left(-\sqrt{\frac{11+4\sqrt5-2\sqrt{50+22\sqrt5}}{3}}\right) ≈ 174.43432°$
	3–3 antiprismatic: $\arccos\left(\frac{1-\sqrt{10+2\sqrt5}}{3}\right) ≈ 159.18651°$
	3–5 join: $\arccos\left(\frac{\sqrt5}{5}\right)+\arccos\left(-\sqrt{\frac{11+4\sqrt5-2\sqrt{50+22\sqrt5}}{3}}\right) ≈ 158.68159°$
	3–5 rotundaic: $\arccos\left(-\sqrt{\frac{5+2\sqrt5}{15}}\right) ≈ 142.62263°$
	3–10: $\arccos\left(-\sqrt{\frac{11+4\sqrt5-2\sqrt{50+22\sqrt5}}{3}}\right) ≈ 95.24664°$
Central density	1
Related polytopes
Army	Gyepro
Regiment	Gyepro
Dual	Pentapentarhombidecapentagonal hemitrapezohedron
Conjugate	Gyroelongated pentagrammic rotunda
Abstract & topological properties
Euler characteristic	2
Surface	Sphere
Orientable	Yes
Genus	0
Properties
Symmetry	H2×I, order 10
Convex	Yes
Nature	Tame

The gyroelongated pentagonal rotunda is one of the 92 Johnson solids (J₂₅). It consists of 5+5+5+5+10 triangles, 1+5 pentagons, and 1 decagon. It can be constructed by attaching a decagonal antiprism to the decagonal base of the pentagonal rotunda.

If a second rotunda is attached to the other decagonal base of the antiprism, the result is the gyroelongated pentagonal birotunda.

Vertex coordinates

A gyroelongated pentagonal rotunda of edge length 1 has the following vertices:

• $\left(±\frac12,\,-\sqrt{\frac{5+2\sqrt5}{20}},\,\sqrt{\frac{5+2\sqrt5}{5}}+h\right),$
• $\left(±\frac{1+\sqrt5}{4},\,\sqrt{\frac{5-\sqrt5}{40}},\,\sqrt{\frac{5+2\sqrt5}{5}}+H\right),$
• $\left(0,\,\sqrt{\frac{5+\sqrt5}{10}},\,\sqrt{\frac{5+2\sqrt5}{5}}+H\right),$
• $\left(±\frac{1+\sqrt5}{4},\,\sqrt{\frac{25+11\sqrt5}{40}},\,\sqrt{\frac{5+\sqrt5}{10}}+H\right),$
• $\left(±\frac{3+\sqrt5}{4},\,-\sqrt{\frac{5+\sqrt5}{40}},\,\sqrt{\frac{5+\sqrt5}{10}}+H\right),$
• $\left(0,\,-\sqrt{\frac{5+2\sqrt5}{5}},\,\sqrt{\frac{5+\sqrt5}{10}}+H\right),$
• $\left(±\frac12,\,±\frac{\sqrt{5+2\sqrt5}}2,\,H\right),$
• $\left(±\frac{3+\sqrt5}4,\,±\sqrt{\frac{5+\sqrt5}8},\,H\right),$
• $\left(±\frac{1+\sqrt5}2,\,0,\,H\right),$
• $\left(±\frac{\sqrt{5+2\sqrt5}}2,\,±\frac12,\,-H\right),$
• $\left(±\sqrt{\frac{5+\sqrt5}8},\,±\frac{3+\sqrt5}4,\,-H\right),$
• $\left(0,\,±\frac{1+\sqrt5}2,\,-H\right),$

where H = $\sqrt{\frac{-4-2\sqrt5+\sqrt{50+22\sqrt{5}}}8}$is the distance between the decagonal antiprism's center and the center of one of its bases.

External links

• Klitzing, Richard. "gyepro".

• Quickfur. "The Gyroelongated Pentagonal Rotunda".

• Wikipedia Contributors. "Gyroelongated pentagonal rotunda".
• McCooey, David. "Gyroelongated Pentagonal Rotunda"