Polarization Losses of 1 Transmitter and Receiver in 3D space

I am trying to compute the polarization losses between one half wave dipole transmitter(Tx) and receiver(Rx). Assuming both the Tx and Rx can be rotated at any arbitrary angle different from each other. However I am unable to compute the Azimuth and Elevation angle differences between the Tx and Rx. As I would like to apply this formula P_Loss=cos(azimuth)*cos(elevation). Any idea how I am able to go about solving this? Thanks.