An angle of intersection of the curves, \( \frac{x^{2}}{a^{2}} + \frac{y^{2}}{b^{2}} = 1 \) and \( x^{2} + y^{2} = ab \), \( a > b \), is:
\( \tan^{-1}\!\left(2\sqrt{ab}\right) \)
\( \tan^{-1}\!\left(\frac{a+b}{\sqrt{ab}}\right) \)
\( \tan^{-1}\!\left(\frac{a-b}{\sqrt{ab}}\right) \)
\( \tan^{-1}\!\left(\frac{a-b}{2\sqrt{ab}}\right) \)