Nope, I meant neither of those two things; I have something else in mind. One math-fun subscriber who prefers to remain anonymous told me that the fact in question is well-known to geometers. Jim Propp On Mon, May 25, 2015 at 4:32 PM, Warren D Smith <warren.wds@gmail.com> wrote:
If the sum S of the 4 corner solid interior angles are used, then Propp is wrong. A flattened sliver tetrahedron has S=0, a flattened regular tet has S=2*pi, etc. there is no constant value.
Propp presumably meant, the 4 tet faces viewed from a point inside; then obviously the "whole sky" has total solid angle 4*pi, the end.
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