What Is a Compound Angle?

Compound of two truncated tetrahedra or truncated compound of two tetrahedra is a concave polyhedron and belongs to star polyhedron

Two compound truncated tetrahedron

Right!

Compound of two truncated tetrahedra or truncated compound of two tetrahedra is a concave polyhedron and belongs to star polyhedron

Compound of two truncated tetrahedra or truncated tetrahedra is a concave polyhedron, belongs to star polyhedron, and is a uniform complex of a middle and half regular polyhedron. The appearance looks like Two truncated tetrahedrons are stuck together, or a star octahedron with truncated vertices. It can be seen from its Coxter mark that one of the two pairs represented by the complex is related to a truncated cube, which is represented in the Coxter mark.