PCP' is a diameter of an ellipse $\displaystyle \frac{x^2}{a^2} + \frac{y^2}{b^2} = 1$ (a > b) & QCQ' is the corresponding diameter of the auxiliary circle, show that the area of the parallelogram formed by the tangent at P, P', Q and Q' is $\displaystyle \frac{8a^2}{(a - b)\sin 2\phi}$ where $\displaystyle \phi$ is the eccentric angle of the point P.

NOTE: C is the centre of the ellipse.