<P> A tetrahedron is a 3 - simplex . Unlike the case of the other Platonic solids, all the vertices of a regular tetrahedron are equidistant from each other (they are the only possible arrangement of four equidistant points in 3 - dimensional space). </P> <P> A tetrahedron is a triangular pyramid, and the regular tetrahedron is self - dual . </P> <P> A regular tetrahedron can be embedded inside a cube in two ways such that each vertex is a vertex of the cube, and each edge is a diagonal of one of the cube's faces . For one such embedding, the Cartesian coordinates of the vertices are </P> <Dl> <Dd> (+ 1, + 1, + 1); </Dd> <Dd> (− 1, − 1, + 1); </Dd> <Dd> (− 1, + 1, − 1); </Dd> <Dd> (+ 1, − 1, − 1). </Dd> </Dl>

Which names a central angle of circle g