I needed to make calculations of the initial bearing between two coordinates described in latitude/longitude. I have found one formulation of this calculation as
Note, I tried formatting the equation with LaTeX but I couldn't see how to do that on stack, using $$ didn't seem to do anything.
This calculation can be found on various sites like link 1 2 3 but I have not been able to find a derivation or a source for the calculation.
I am looking for a derivation or an explanation of the derivation of this calculation.