What is the name of this formula? There is 3d angle addition formula for which I would like to know what it is called in the literature:
Given two vectors $\vec v_1$, $\vec v_2$ at (physicist's) angles $(\theta_1,\,\phi_1)$ and $(\theta_2,\,\phi_2)$, the angle $\Theta$ between the two vectors is given by:
$$\cos \Theta=\cos \theta_1 \cos\theta_2+\sin\theta_1\sin\theta_2\cos(\phi_1-\phi_2)$$
What is the name of this formula?

Apparently, my comment answered the question. I'll convert the comment to a formal answer in order to get the question out of the Unanswered queue.

The formula looks an awful lot like the Spherical Law of Cosines.

