Given a sphere with a specified radius, and two perpendicular arcs produced by angles, phi and theta.
To be clear, phi and theta are the angles which give rise to the arcs which meet at a right angle. I placed the labels, phi and theta, on the actual arcs because it gets crowded near the center of the sphere. I am looking for the interior angle which gives rise to the oblique arc on the sphere's surface.
I read these links:
but the derivation of an answer eludes me.
I realize that spending time to answer a question so fundamental and which has probably been answered clearly in some text is a waste of bandwidth. So maybe someone knows of a clear, simple exposition of this problem to which I can be referred?