Every Tetrahedron has a 3-vertex Quasigeodesic
arXiv:2109.07444
Abstract
We prove that every tetrahedron T has a simple, closed quasigeodesic that passes through three vertices of T. Equivalently, every T has a face whose "exterior angles" are at most pi.
10 pages, 3 figures, 3 references. V2: Removed tangential claim concerning 2-vertex quasigeodesics