- Enneacross
An enneacross, is a regular
9-polytope with 18 vertices, 144 edges, 672 triangle faces, 2016 octahedron cells, 40325-cell s "4-faces", 5376 "5-faces", 4608 "6-faces", 2304 "7-faces", and 512 "8-faces".It is one of an infinite family of polytopes, called
cross-polytope s or "orthoplexes". The dual polytope is the 9-hypercube orenneract .The name "enneacross" is derived from combining the family name "cross polytope" with "ennea" for nine (dimensions) in Greek.
Construction
There are two
Coxeter group s associated with the "enneacross", one regular, dual of theenneract with the C9 or [4,37] symmetry group, and a lower symmetry with two copies of 8-simplex facets, alternating, with the D9 or [36,1,1] symmetry group.Cartesian coordinates
Cartesian coordinates for the vertices of an enneacross, centered at the origin are: (±1,0,0,0,0,0,0,0,0), (0,±1,0,0,0,0,0,0,0), (0,0,±1,0,0,0,0,0,0), (0,0,0,±1,0,0,0,0,0), (0,0,0,0,±1,0,0,0,0), (0,0,0,0,0,±1,0,0,0), (0,0,0,0,0,0,±1,0,0), (0,0,0,0,0,0,0,±1,0), (0,0,0,0,0,0,0,0,±1)Every vertex pair is connected by an edge, except opposites.
See also
* Other regular
9-polytope s:
**9-simplex (decayotton) - {38}
**9-cube (enneract) - {4,37}
**9-demicube (demienneract) - {31,6,1}
* Others in thecross-polytope family
**Octahedron - {3,4}
**Hexadecachoron - {3,3,4}
**Pentacross - {33,4}
**Hexacross - {34,4}
**Heptacross - {35,4}
**Octacross - {36,4}
**Enneacross - {37,4}
**Decacross - {38,4}External links
*GlossaryForHyperspace | anchor=Cross | title=Cross polytope
* [http://members.cox.net/hedrondude/topes.htm Polytopes of Various Dimensions]
* [http://tetraspace.alkaline.org/glossary.htm Multi-dimensional Glossary]
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