An initial investigation into the geometrical meaning of the (pseudo-) inverses of the line matrices for the edges of platonic polyhedra

Abstract

It is well known that there are five regular (Platonic) polyhedra: the tetrahedron, the hexahedron (cube), the octahedron, the icosahedron and the dodecahedron. Each of these polyhedra has an associated dual polyhedron which is also Platonic. By considering the Platonic polyhedra to be constructed from lines, and then representing the lines in terms of both ray and axis coordinates, a further aspect of this duality is exposed. This is the duality of poles and polars associated with projective configurations of points, lines and planes. This paper shows that a line matrix may be constructed for any regular polyhedron, in such a way that its columns represent the normalized ray coordinates of the edges of the polyhedron. The (pseudo-) inverse of this line matrix may then be constructed, the rows of which represent the normalized axis coordinates of the corresponding dual polyhedron.

Keywords

Platonic polyhedra line matrices pseudo-inverse ray coordinates axis coordinates

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