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Disdyakis dodecahedron

From Wikipedia, the free encyclopedia
Catalan solid with 48 faces
Disdyakis dodecahedron
Disdyakis dodecahedron
(rotating and3D model)
TypeCatalan solid
Conway notationmC
Coxeter diagram
Face polygon
scalene triangle
Faces48
Edges72
Vertices26 = 6 + 8 + 12
Face configurationV4.6.8
Symmetry groupOh, B3, [4,3], *432
Dihedral angle155° 4' 56"
arccos(71+12297){\displaystyle \arccos(-{\frac {71+12{\sqrt {2}}}{97}})}
Dual polyhedron
truncated cuboctahedron
Propertiesconvex,face-transitive
Disdyakis dodecahedron
net

Ingeometry, adisdyakis dodecahedron, (alsohexoctahedron,[1]hexakis octahedron,octakis cube,octakis hexahedron,kisrhombic dodecahedron[2]) ord48, is aCatalan solid with 48 faces and the dual to theArchimedeantruncated cuboctahedron. As such it isface-transitive but with irregular face polygons. It resembles an augmentedrhombic dodecahedron. Replacing each face of the rhombic dodecahedron with a flat pyramid results in theKleetope of the rhombic dodecahedron, which looks almost like the disdyakis dodecahedron, and istopologically equivalent to it.[a] The net of therhombic dodecahedral pyramid also shares the same topology.

Symmetry

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It has Ohoctahedral symmetry. Its collective edges represent the reflection planes of the symmetry. It can also be seen in the corner and mid-edge triangulation of the regular cube and octahedron, and rhombic dodecahedron.


Disdyakis
dodecahedron

Deltoidal
icositetrahedron

Rhombic
dodecahedron

Hexahedron

Octahedron
Spherical polyhedron
(seerotating model)Orthographic projections from 2-, 3- and 4-fold axes

The edges of a spherical disdyakis dodecahedron belong to 9great circles. Three of them form a spherical octahedron (gray in the images below). The remaining six form three squarehosohedra (red, green and blue in the images below). They all correspond tomirror planes - the former indihedral [2,2], and the latter intetrahedral [3,3] symmetry. A spherical disdyakis dodecahedron can be thought of as thebarycentric subdivision of thespherical cube or of thespherical octahedron.[3]

Stereographic projections
2-fold3-fold4-fold

Cartesian coordinates

[edit]

Let a=11+22 0.261,  b=12+32 0.160,  c=13+32 0.138{\displaystyle ~a={\frac {1}{1+2{\sqrt {2}}}}~{\color {Gray}\approx 0.261},~~b={\frac {1}{2+3{\sqrt {2}}}}~{\color {Gray}\approx 0.160},~~c={\frac {1}{3+3{\sqrt {2}}}}~{\color {Gray}\approx 0.138}}.
Then theCartesian coordinates for the vertices of a disdyakis dodecahedron centered at the origin are:

 permutations of (±a, 0, 0)  (vertices of an octahedron)
  permutations of (±b, ±b, 0)  (vertices of acuboctahedron)
  (±c, ±c, ±c)  (vertices of a cube)

Convex hulls
Combining an octahedron, cube, and cuboctahedron to form the disdyakis dodecahedron. The convex hulls for these vertices[4] scaled by1/a{\displaystyle 1/a} result in Cartesian coordinates of unitcircumradius, which are visualized in the figure below:
Combining an octahedron, cube, and cuboctahedron to form the disdyakis dodecahedron

Dimensions

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If its smallest edges have lengtha, its surface area and volume are

A=67783+4362a2V=173(2194+15132)a3{\displaystyle {\begin{aligned}A&={\tfrac {6}{7}}{\sqrt {783+436{\sqrt {2}}}}\,a^{2}\\V&={\tfrac {1}{7}}{\sqrt {3\left(2194+1513{\sqrt {2}}\right)}}a^{3}\end{aligned}}}

The faces are scalene triangles. Their angles arearccos(161122) 87.201{\displaystyle \arccos {\biggl (}{\frac {1}{6}}-{\frac {1}{12}}{\sqrt {2}}{\biggr )}~{\color {Gray}\approx 87.201^{\circ }}},arccos(34182) 55.024{\displaystyle \arccos {\biggl (}{\frac {3}{4}}-{\frac {1}{8}}{\sqrt {2}}{\biggr )}~{\color {Gray}\approx 55.024^{\circ }}} andarccos(112+122) 37.773{\displaystyle \arccos {\biggl (}{\frac {1}{12}}+{\frac {1}{2}}{\sqrt {2}}{\biggr )}~{\color {Gray}\approx 37.773^{\circ }}}.

Orthogonal projections

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The truncated cuboctahedron and its dual, thedisdyakis dodecahedron can be drawn in a number of symmetric orthogonal projective orientations. Between a polyhedron and its dual, vertices and faces are swapped in positions, and edges are perpendicular.

Projective
symmetry
[4][3][2][2][2][2][2]+
Image
Dual
image

Related polyhedra and tilings

[edit]
Polyhedra similar to the disdyakis dodecahedron are duals to theBowtie octahedron and cube, containing extra pairs triangular faces .[5]

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

Uniform octahedral polyhedra
Symmetry: [4,3],(*432)[4,3]+
(432)
[1+,4,3] = [3,3]
(*332)
[3+,4]
(3*2)
{4,3}t{4,3}r{4,3}
r{31,1}
t{3,4}
t{31,1}
{3,4}
{31,1}
rr{4,3}
s2{3,4}
tr{4,3}sr{4,3}h{4,3}
{3,3}
h2{4,3}
t{3,3}
s{3,4}
s{31,1}

=

=

=
=
or
=
or
=





Duals to uniform polyhedra
V43V3.82V(3.4)2V4.62V34V3.43V4.6.8V34.4V33V3.62V35

It is a polyhedra in a sequence defined by theface configuration V4.6.2n. This group is special for having all even number of edges per vertex and form bisecting planes through the polyhedra and infinite lines in the plane, and continuing into the hyperbolic plane for anyn ≥ 7.

With an even number of faces at every vertex, these polyhedra and tilings can be shown by alternating two colors so all adjacent faces have different colors.

Each face on these domains also corresponds to the fundamental domain of asymmetry group with order 2,3,n mirrors at each triangle face vertex.

*n32 symmetry mutation of omnitruncated tilings: 4.6.2n
Sym.
*n32
[n,3]
SphericalEuclid.Compact hyperb.Paraco.Noncompact hyperbolic
*232
[2,3]
*332
[3,3]
*432
[4,3]
*532
[5,3]
*632
[6,3]
*732
[7,3]
*832
[8,3]
*∞32
[∞,3]
 
[12i,3]
 
[9i,3]
 
[6i,3]
 
[3i,3]
Figures
Config.4.6.44.6.64.6.84.6.104.6.124.6.144.6.164.6.∞4.6.24i4.6.18i4.6.12i4.6.6i
Duals
Config.V4.6.4V4.6.6V4.6.8V4.6.10V4.6.12V4.6.14V4.6.16V4.6.∞V4.6.24iV4.6.18iV4.6.12iV4.6.6i
*n42 symmetry mutation of omnitruncated tilings: 4.8.2n
Symmetry
*n42
[n,4]
SphericalEuclideanCompact hyperbolicParacomp.
*242
[2,4]
*342
[3,4]
*442
[4,4]
*542
[5,4]
*642
[6,4]
*742
[7,4]
*842
[8,4]...
*∞42
[∞,4]
Omnitruncated
figure

4.8.4

4.8.6

4.8.8

4.8.10

4.8.12

4.8.14

4.8.16

4.8.∞
Omnitruncated
duals

V4.8.4

V4.8.6

V4.8.8

V4.8.10

V4.8.12

V4.8.14

V4.8.16

V4.8.∞

See also

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Notes

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  1. ^Despite their resemblance, no subset of the disdyakis dodecahedron's vertices forms a rhombic dodecahedron (see#Cartesian coordinates), and therefore, the former is not the Kleetope of the latter. The "rhombic" bases of the pyramids of the disdyakis dodecahedron are in fact not even planar; for example, the vertices of one such rhombus are (a, 0, 0), (0, a, 0), (c, c, c), (c, c, -c) (again, see#Cartesian coordinates for the values of a and c), with diagonal midpoints (√2)×(a, a, 0) and (c, c, 0), which do not coincide.

References

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  1. ^"Keyword: "forms" | ClipArt ETC".
  2. ^Conway, Symmetries of things, p.284
  3. ^Langer, Joel C.; Singer, David A. (2010), "Reflections on the lemniscate of Bernoulli: the forty-eight faces of a mathematical gem",Milan Journal of Mathematics,78 (2):643–682,doi:10.1007/s00032-010-0124-5,MR 2781856
  4. ^Koca, Mehmet; Ozdes Koca, Nazife; Koc, Ramazon (2010). "Catalan Solids Derived From 3D-Root Systems and Quaternions".Journal of Mathematical Physics.51 (4).arXiv:0908.3272.doi:10.1063/1.3356985.
  5. ^Symmetrohedra: Polyhedra from Symmetric Placement of Regular Polygons Craig S. Kaplan
  • Williams, Robert (1979).The Geometrical Foundation of Natural Structure: A Source Book of Design. Dover Publications, Inc.ISBN 0-486-23729-X. (Section 3-9)
  • The Symmetries of Things 2008, John H. Conway, Heidi Burgiel, Chaim Goodman-Strauss,ISBN 978-1-56881-220-5[1] (Chapter 21, Naming the Archimedean and Catalan polyhedra and tilings, page 285, kisRhombic dodecahedron)

External links

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Triakis tetrahedron
(Needle)

Triakis tetrahedron
(Kis)

Triakis octahedron
(Needle)

Tetrakis hexahedron
(Kis)

Triakis icosahedron
(Needle)

Pentakis dodecahedron
(Kis)

Rhombic hexahedron
(Join)

Rhombic dodecahedron
(Join)

Rhombic triacontahedron
(Join)

Deltoidal dodecahedron
(Ortho)

Disdyakis hexahedron
(Meta)

Deltoidal icositetrahedron
(Ortho)

Disdyakis dodecahedron
(Meta)

Deltoidal hexecontahedron
(Ortho)

Disdyakis triacontahedron
(Meta)

Pentagonal dodecahedron
(Gyro)

Pentagonal icositetrahedron
(Gyro)

Pentagonal hexecontahedron
(Gyro)
Convexpolyhedra
Platonic solids(regular)
Catalan solids
(duals of Archimedean)
Dihedral regular
Dihedral uniform
duals:
Dihedral others
Degenerate polyhedra are initalics.
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