I've an ellipse that is rotated and not centered in the origin. Hence, I've an ellipse equation that is in the form of:
\begin{equation} \frac{((x-h)cos(\phi) + (y-k)sin(\phi))^2}{a^2} + \frac{((x-h)sin(\phi) - (y-k)cos(\phi))^2}{b^2} = 1 \end{equation} Suppose that I know the foci, the center and a and b, how can find $\phi$ ?