Question

Set of triangle with four vertices is empty set

Answer 1

Answer:

In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. ... Still ...

3.3.3 (Vertex figure): Self-dual; (dual polyhedron)

Faces by sides: 4

Dihedral angle: 70.528779° = arccos(1⁄3)

Face configuration: V3.3.3