tetrahedron(redirected from Tetrahedroid)
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, closed solid bounded by plane faces; each face of a polyhedron is a polygon. A cube is a polyhedron bounded by six polygons (in this case squares) meeting at right angles.
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(or triangular pyramid), a polyhedron with four triangular faces, six edges, and four vertices. At each vertex three edges intersect. The regular tetrahedron (Figure 1) is one
of the five regular polyhedrons. If a is the length of an edge of a regular tetrahedron, the volume of the tetrahedron is .