Hi.

Can anybody help me with the solution of the next integral:

$\displaystyle \int_{\phi_0}^{\phi} \cos\theta\sqrt{\sin^2 \theta+\left(\frac{d\theta}{d\phi}\right )^2} d \phi$

where $\displaystyle \theta=\theta(\phi)$.

The problem is that don't know the relation between $\displaystyle \theta$ and $\displaystyle \phi$.