Related Problems in Spherical and Solid Geometry

Abstract: A problem that is simple to state in the context of spherical geometry, and that seems rather interesting, appears to have been unexamined to date in the mathematical literature. The problem can also be recast as a problem in the real projective plane. The problem on the sphere involves four great circles and their intersections. A substantial claim is made concerning this problem, and subsequently proved by relating the spherical problem to a compelling problem in solid geometry. This latter problem essentially concerns relationships between the angles of a tetrahedron, and has practical applications, particularly in connection with the Perspective 3-Point (Pose) Problem.