Q. If $\tan \theta_1 \cdot \tan \theta_2=-\frac{ a ^2}{ b ^2}$ then the chord joining two points $\theta_1 \& \theta_2$ on the ellipse $\frac{ x ^2}{ a ^2}+\frac{ y ^2}{ b ^2}=1$ will subtend a right angle at :
Conic Sections
Solution: