Rectified 5-cell

Seen in a configuration matrix, all incidence counts between elements are shown. The diagonal f-vector numbers are derived through the Wythoff construction, dividing the full group order of a subgroup order by removing one mirror at a time. == Structure ==

Together with the simplex and 24-cell, this shape and its dual (a polytope with ten vertices and ten triangular bipyramid facets) was one of the first 2-simple 2-simplicial 4-polytopes known. This means that all of its two-dimensional faces, and all of the two-dimensional faces of its dual, are triangles. In 1997, Tom Braden found another dual pair of examples, by gluing two rectified 5-cells together; since then, infinitely many 2-simple 2-simplicial polytopes have been constructed. == Semiregular polytope ==

It is one of three semiregular 4-polytopes made of two or more cells which are Platonic solids, discovered by Thorold Gosset in his 1900 paper. He called it a tetroctahedric for being made of tetrahedron and octahedron cells. E. L. Elte identified it in 1912 as a semiregular polytope, labeling it as tC5. == Alternate names ==

• Tetroctahedric (Thorold Gosset) • Dispentachoron • Rectified 5-cell (Norman W. Johnson) • Rectified 4-simplex • Fully truncated 4-simplex • Rectified pentachoron (Acronym: rap) (Jonathan Bowers) • Ambopentachoron (Neil Sloane & John Horton Conway) • (5,2)-hypersimplex (the convex hull of five-dimensional (0,1)-vectors with exactly two ones) == Images ==

The Cartesian coordinates of the vertices of an origin-centered rectified 5-cell having edge length 2 are: More simply, the vertices of the rectified 5-cell can be positioned on a hyperplane in 5-space as permutations of (0,0,0,1,1) or (0,0,1,1,1). These construction can be seen as positive orthant facets of the rectified pentacross or birectified penteract respectively. == Related 4-polytopes ==

The rectified 5-cell is the vertex figure of the 5-demicube, and the edge figure of the uniform 221 polytope. Compound of the rectified 5-cell and its dual The convex hull the rectified 5-cell and its dual (of the same long radius) is a nonuniform polychoron composed of 30 cells: 10 tetrahedra, 20 octahedra (as triangular antiprisms), and 20 vertices. Its vertex figure is a triangular bifrustum. Pentachoron polytopes The rectified 5-cell is one of 9 Uniform 4-polytopes constructed from the [3,3,3] Coxeter group. Semiregular polytopes The rectified 5-cell is second in a dimensional series of semiregular polytopes. Each progressive uniform polytope is constructed as the vertex figure of the previous polytope. Thorold Gosset identified this series in 1900 as containing all regular polytope facets, containing all simplexes and orthoplexes (tetrahedrons and octahedrons in the case of the rectified 5-cell). The Coxeter symbol for the rectified 5-cell is 021. Isotopic polytopes == Notes ==