Pentagrammic prism

Uniform Pentagrammic prism

Type	Prismatic uniform polyhedron
Elements	F = 7, E = 15 V = 10 (χ = 2)
Faces by sides	5{4}+2{⁵/₂}
Schläfli symbol	t{2,⁵/₂} or {5/2}x{}
Wythoff symbol	2 ⁵/₂ \| 2
Coxeter diagram
Symmetry	D_5h, [5,2], (*522), order 20
Rotation group	D₅, [5,2]⁺, (522), order 10
Index references	U_78(a)
Dual	Pentagrammic dipyramid
Properties	nonconvex
Vertex figure 4.4.⁵/₂

In geometry, the pentagrammic prism is one in an infinite set of nonconvex prisms formed by square sides and two regular star polygon caps, in this case two pentagrams.

This polyhedron is identified with the indexed name U₇₈ as a uniform polyhedron.

It is a special case of a right prism with a pentagram as base, which in general has rectangular non-base faces.

Note that the pentagram face has an ambiguous interior because it is self-intersecting. The central pentagon region can be considered interior or exterior depending on how interior is defined. One definition of interior is the set of points that have a ray that crosses the boundary an odd number of times to escape the perimeter.

In either case, it is best to show the pentagram boundary line to distinguish it from a concave decagon.

Gallery

An alternative representation with hollow centers to the pentagrams.	The pentagrammic dipyramid is the dual to the Pentagrammic prism

External links

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