If the product of the perpendicular distances from any point on the hyperbola…
- $3$
- $6$
- $8$
- $12$
Solution

$P Q=\left|\frac{a b \sec \theta-a b \tan \theta}{\sqrt{b^2+a^2}}\right|$ and $P R=\left|\frac{a b \sec \theta+a b \tan \theta}{\sqrt{b^2+a^2}}\right|$ According to question, $\frac{a b(\sec \theta-\tan \theta)}{\sqrt{a^2+b^2}} \times \frac{a b(\sec \theta+\tan \theta)}{\sqrt{a^2+b^2}}=6$ $\Rightarrow \frac{a^2 b^2\left(\sec ^2 \theta-\tan ^2 \theta\right)}{\left(a^2+b^2\right)}=6$ $\Rightarrow \quad \frac{a^2 b^2}{a^2 e^2}=6 \quad\left[\because a^2+b^2=a^2 e^2\right]$ $\begin{array}{ll}\Rightarrow & b^2=6 \times e^2=6 \times 3=18 \\ \because & a^2+b^2=a^2 e^2\end{array}$ $\therefore \quad a^2+18=a^2 \times 3 \Rightarrow a^2=9$ $\Rightarrow \quad a=3$ Length of transverse axis $=2 \times 3=6$
Asked in: AP EAMCET 2022 (07 Jul Shift 1)