# Great rhombicuboctahedron

(Redirected from Girco)
Great rhombicuboctahedron
Rank3
TypeUniform
Notation
Bowers style acronymGirco
Coxeter diagramx4x3x ()
Conway notationbC
Stewart notationK4
Elements
Faces12 squares, 8 hexagons, 6 octagons
Edges24+24+24
Vertices48
Vertex figureScalene triangle, edge lengths 2, 3, 2+2
Measures (edge length 1)
Circumradius${\displaystyle {\frac {\sqrt {13+6{\sqrt {2}}}}{2}}\approx 2.31761}$
Volume${\displaystyle 2(11+7{\sqrt {2}})\approx 41.79899}$
Dihedral angles6–4: ${\displaystyle \arccos \left(-{\frac {\sqrt {6}}{3}}\right)\approx 144.73561^{\circ }}$
8–4: 135°
8–6: ${\displaystyle \arccos \left(-{\frac {\sqrt {3}}{3}}\right)\approx 125.26439^{\circ }}$
Central density1
Number of external pieces26
Level of complexity6
Related polytopes
ArmyGirco
RegimentGirco
DualDisdyakis dodecahedron
ConjugateQuasitruncated cuboctahedron
Abstract & topological properties
Flag count288
Euler characteristic2
SurfaceSphere
OrientableYes
Genus0
Properties
SymmetryB3, order 48
Flag orbits6
ConvexYes
NatureTame

The great rhombicuboctahedron or girco, also commonly known as the truncated cuboctahedron, is one of the 13 Archimedean solids. It consists of 12 squares, 8 hexagons, and 6 octagons, with one of each type of face meeting per vertex. It can be obtained by cantitruncation of the cube or octahedron, or equivalently by truncating the vertices of a cuboctahedron and then adjusting the edge lengths to be all equal.

This is one of three Wythoffian non-prismatic polyhedra with a Coxeter diagram having all ringed nodes, the other two being the great rhombitetratetrahedron and the great rhombicosidodecahedron.

It can be alternated into the snub cube after equalizing edge lengths.

## Naming

Rhombi refers to the twelve square faces on the axis of the rhombic dodecahedron, cub(e) refers to the six faces on the axis of the cube, and octahedron for the eight hexagons on the axis of the octahedron.

Alternate names include:

• Truncated cuboctahedron (a translation of Kepler's Latin name), because it can be derived by truncating the cuboctahedron. However, it is not a true truncation of the rhombicuboctahedron, as a true truncation would result in rectangles rather than squares. Kepler used a different word for this sense of "truncated", but it was lost in translation.
• Rhombitruncated cuboctahedron (similar to the above, but also refers to the planes of the truncated faces).
• Great rhombcuboctahedron (no "i") - alternate spelling.

## Vertex coordinates

A great rhombicuboctahedron of edge length 1 has vertex coordinates given by all permutations of:

• ${\displaystyle \left(\pm {\frac {1+2{\sqrt {2}}}{2}},\,\pm {\frac {1+{\sqrt {2}}}{2}},\,\pm {\frac {1}{2}}\right).}$

## Representations

A great rhombicuboctahedron has the following Coxeter diagrams:

• x4x3x (full symmetry)
• xxwwxx4xuxxux&#xt (B2 axial, octagon-first)
• wx3xx3xw&#zx (A3 symmetry, as hull of two inverse great rhombitetratetrahedra)
• Xwx xxw4xux&#zx (B2×A1 symmetry)
• xxuUxwwx3xwwxUuxx&#xt (A2 axial, hexagon-first)

## Semi-uniform variant

The great rhombicuboctahedron has a semi-uniform variant of the form x4y3z that maintains its full symmetry. This variant has 6 ditetragons, 8 ditrigons, and 12 rectangles as faces.

With edges of length a (ditetragon-rectangle), b (ditetragon-ditrigon), and c (ditrigon-rectangle), its circumradius is given by ${\displaystyle {\frac {\sqrt {3a^{2}+4b^{2}+2c^{2}+4bc+(4ab+2ac){\sqrt {2}}}}{2}}}$ and its volume is given by ${\displaystyle a^{3}+6ab^{2}+12abc+3ac^{2}+(9a^{2}b+9a^{2}c+5b^{3}+12b^{2}c+6bc^{2}+c^{3}){\frac {\sqrt {2}}{3}}}$.

It has coordinates given by all permutations of:

• ${\displaystyle \left(\pm {\frac {a+(b+c){\sqrt {2}}}{2}},\,\pm {\frac {a+b{\sqrt {2}}}{2}},\,\pm {\frac {a}{2}}\right)}$.