A chamfered tertrahedron, also known as the alternate truncated cube, is a polyhedron obtained by chamfering a regular tetrahedron. The illustration above shows increasing amounts of chamfering applied to the regular tetrahedron.
It is a (non-regular) decahedron.
An equilateral chamfered tetrahedron may be constructed by appropriate choice of the edge length ratio for chamfering. The unit equilateral chamfered tetrahedron has surface area and volume
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(1)
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(2)
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and is implemented in the Wolfram Language as PolyhedronData["EquilateralChamferedTetrahedron"].
