A scalene triangle abc might also be employed, or a tetrahedron.
The tetrahedron, having four equilateral triangles as faces.
Its head was a pyramid, a tetrahedron; its length vanished in the further darkness.
It occurs crystallized in the form of the tetrahedron, also massive and disseminated.
Round Mars describe a tetrahedron; the sphere including this will be Jupiter.
There were characters in Nansalese at each point of the tetrahedron, and other characters engraved in a circle around it.
These give the solid angles of the tetrahedron, the octahedron and the icosahedron.
From the sides of the hollow square sprang long arms of spheres, each tipped by a tetrahedron.
Each of the four depressed areas forms a side of our tetrahedron and is occupied by an ocean.
This four dimensional figure may be generated by moving the tetrahedron in the direction of the fourth dimension, as in Fig. 12.
solid figure contained by four triangular surfaces, 1560s, from Late Greek tetraedron, originally neuter of tetraedros (adj.) "four-sided," from tetra- "four" + hedra "seat, base, chair, face of a geometric solid," from PIE root *sed- (1) "to sit" (see sedentary).