Helllo, I'm new here. I will try this great place to get my answer. I have a next problem:
$$\vartheta = \arctan(K \tan \varphi)$$
$K > 0$
Where $K$ is a constant. If $K = 1$ then $\vartheta = \varphi$, but I can't find more simple answer for $\vartheta$ if $K \neq 1$. Maybe someone will be able to help me out, if it is even possbile.