We know that the sum of angles of a triangle equals the straight angle (180 degrees).
Can we convert a 2D theorem to 3D?
e. g. We can generalize the triangle to a tetrahedron, angles of the triangle to the dihedral angles of tetrahedron. Do we know or can we calculate the sum of dihedral angles of the tetrahedron?
The similar theorem for tetrahedrons is that the sum of its solid angles plus twice the sum of its dihedral angles is $4\pi$
See here