Completing a Tetrahedron to a Parallelepiped

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The Wolfram Demonstrations Project contains thousands of free interactive visualizations, with new entries added daily.
This Demonstration shows a completion of a tetrahedron T to a parallelepiped P. The four vertices of T are vertices of P, and the edges of T become four diagonals on the faces of P.
Contributed by: Izidor Hafner
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