PCP' is a diameter of an ellipse \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 \frac{8a^2}{(a - b)\sin 2\phi} where \phi is the eccentric angle of the point P.

NOTE: C is the centre of the ellipse.