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[5] The regular heptagon belongs to the D 7h point group (Schoenflies notation), order 28. The symmetry elements are: a 7-fold proper rotation axis C 7, a 7-fold improper rotation axis, S 7, 7 vertical mirror planes, σ v, 7 2-fold rotation axes, C 2, in the plane of the heptagon and a horizontal mirror plane, σ h, also in the heptagon's plane ...
It follows that all vertices are congruent, and the polyhedron has a high degree of reflectional and rotational symmetry. ... 7: 5{4} +2{5} Hexagonal prism: 4.4.6:
A regular pentagon has 5 equal edges and 5 equal angles. ... and the points where two of the edges meet are the polygon's vertices ... 5: pentagon: 6: hexagon: 7 ...
By a theorem of Descartes, this is equal to 4 π divided by the number of vertices (i.e. the total defect at all vertices is 4 π). The three-dimensional analog of a plane angle is a solid angle . The solid angle, Ω , at the vertex of a Platonic solid is given in terms of the dihedral angle by
There are 34 topologically distinct convex heptahedra, excluding mirror images. [2] ( Two polyhedra are "topologically distinct" if they have intrinsically different arrangements of faces and vertices, such that it is impossible to distort one into the other simply by changing the lengths of edges or the angles between edges or faces.)
This polyhedron is topologically related as a part of a sequence of cantellated polyhedra with vertex figure (3.4.n.4), which continues as tilings of the hyperbolic plane. These vertex-transitive figures have (*n32) reflectional symmetry .
All vertices are valence-6 except the 12 centered at the original vertices which are valence 5. A geodesic polyhedron is a convex polyhedron made from triangles. They usually have icosahedral symmetry, such that they have 6 triangles at a vertex, except 12 vertices which have 5 triangles.
The hexagonal tiling honeycomb, {6,3,3}, has hexagonal tiling, {6,3}, facets with vertices on a horosphere. One such facet is shown in as seen in this Poincaré disk model . In H 3 hyperbolic space , paracompact regular honeycombs have Euclidean tiling facets and vertex figures that act like finite polyhedra.