Hi all!

I have a problem which I need to solve, but I can't be sure that there is a simple solution.

I have:

$\displaystyle \frac{cos^2(\phi(x))}{(1-cos(\phi(x)))} = f(x)$

and I want to write $\displaystyle \phi(x)$ as:

$\displaystyle \phi(x) = g(x)$.

The problem looks quite nice, and slightly familiar, but I can't for the life of me work it out. My trigonometry has deserted me.