Truncated cube

{{Short description|Archimedean solid with 14 regular faces}}

{{Semireg polyhedra db|Semireg polyhedron stat table|tC}}

File:Truncated cube.stl

In geometry, the truncated cube, or truncated hexahedron, is an Archimedean solid. It has 14 regular faces (6 octagonal and 8 triangular), 36 edges, and 24 vertices.

If the truncated cube has unit edge length, its dual triakis octahedron has edges of lengths {{math|2}} and {{math|δS +1}},

where δS is the silver ratio, {{sqrt|2}} +1.

Area and volume

The area A and the volume V of a truncated cube of edge length a are:

:\begin{align}

A &= 2\left(6+6\sqrt{2}+\sqrt{3}\right)a^2 &&\approx 32.434\,6644a^2 \\

V &= \frac{21+14\sqrt{2}}{3}a^3 &&\approx 13.599\,6633a^3. \end{align}

Orthogonal projections

The truncated cube has five special orthogonal projections, centered, on a vertex, on two types of edges, and two types of faces: triangles, and octagons. The last two correspond to the B2 and A2 Coxeter planes.

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|+ Orthogonal projections

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Octagon

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Triangle

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Spherical tiling

The truncated cube can also be represented as a spherical tiling, and projected onto the plane via a stereographic projection. This projection is conformal, preserving angles but not areas or lengths. Straight lines on the sphere are projected as circular arcs on the plane.

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Orthographic projection

!colspan=2|Stereographic projections

Cartesian coordinates

File:Icosidecahedron_in_truncated_cube.png dissected with a central vertex into triangles and pentagons, creating a topological icosidodecahedron]]

Cartesian coordinates for the vertices of a truncated hexahedron centered at the origin with edge length 2{{sfrac|1|δS}} are all the permutations of

:(±{{sfrac|1|δS}}, ±1, ±1),

where δS={{sqrt|2}}+1.

If we let a parameter ξ= {{sfrac|1|δS}}, in the case of a Regular Truncated Cube, then the parameter ξ can be varied between ±1. A value of 1 produces a cube, 0 produces a cuboctahedron, and negative values produces self-intersecting octagrammic faces.

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If the self-intersected portions of the octagrams are removed, leaving squares, and truncating the triangles into hexagons, truncated octahedra are produced, and the sequence ends with the central squares being reduced to a point, and creating an octahedron.

Dissection

File:Dissected_truncated_cube.png

The truncated cube can be dissected into a central cube, with six square cupolae around each of the cube's faces, and 8 regular tetrahedra in the corners. This dissection can also be seen within the runcic cubic honeycomb, with cube, tetrahedron, and rhombicuboctahedron cells.

This dissection can be used to create a Stewart toroid with all regular faces by removing two square cupolae and the central cube. This excavated cube has 16 triangles, 12 squares, and 4 octagons.B. M. Stewart, Adventures Among the Toroids (1970) {{isbn|978-0-686-11936-4}}{{Cite web|url=http://www.doskey.com/polyhedra/Stewart05.html|title = Adventures Among the Toroids - Chapter 5 - Simplest (R)(A)(Q)(T) Toroids of genus p=1}}

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Vertex arrangement

It shares the vertex arrangement with three nonconvex uniform polyhedra:

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Truncated cube

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Nonconvex great rhombicuboctahedron

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Great cubicuboctahedron

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Great rhombihexahedron

Related polyhedra

The truncated cube is related to other polyhedra and tilings in symmetry.

The truncated cube is one of a family of uniform polyhedra related to the cube and regular octahedron.

{{Octahedral truncations}}

= Symmetry mutations=

This polyhedron is topologically related as a part of sequence of uniform truncated polyhedra with vertex configurations (3.2n.2n), and [n,3] Coxeter group symmetry, and a series of polyhedra and tilings n.8.8.

{{Truncated figure1 small table}}

{{Truncated figure4 table}}

= Alternated truncation=

{{multiple image

| align = right | total_width = 400

| image1 = Polyhedron 4a.png

| image2 = Polyhedron chamfered 4a.png

| image3 = Polyhedron truncated 6.png

| footer = Tetrahedron, its edge truncation, and the truncated cube

}}

Truncating alternating vertices of the cube gives the chamfered tetrahedron, i.e. the edge truncation of the tetrahedron.

The truncated triangular trapezohedron is another polyhedron which can be formed from cube edge truncation.

Related polytopes

The truncated cube, is second in a sequence of truncated hypercubes:

{{Truncated hypercube polytopes}}

Truncated cubical graph

{{Infobox graph

| name = Truncated cubical graph

| image = 240px

| image_caption = 4-fold symmetry Schlegel diagram

| namesake =

| vertices = 24

| edges = 36

| automorphisms = 48

| radius =

| diameter =

| girth =

| chromatic_number = 3

| chromatic_index =

| fractional_chromatic_index =

| properties = Cubic, Hamiltonian, regular, zero-symmetric

}}

In the mathematical field of graph theory, a truncated cubical graph is the graph of vertices and edges of the truncated cube, one of the Archimedean solids. It has 24 vertices and 36 edges, and is a cubic Archimedean graph.{{citation|last1=Read|first1=R. C.|last2=Wilson|first2=R. J.|title=An Atlas of Graphs|publisher=Oxford University Press|year= 1998|page=269}}

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Orthographic

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See also

References

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  • {{The Geometrical Foundation of Natural Structure (book)}} (Section 3-9)
  • Cromwell, P. Polyhedra, CUP hbk (1997), pbk. (1999). Ch.2 p. 79-86 Archimedean solids