Question

The length of transverse axis of the rectangular hyperbola $xy=18$ is

• A. $6$
• B. $12$
• C. $18$
• D. $3$

Answer 1

The correct option is D $3$

Given, $xy=18....\left(i\right)$
On comparing Eq. (i) by $xy=c^2$, we get
$c^2=18$
$\because a^2=\frac{c^2}{2}$
$\Rightarrow a^2=\frac{18}{2}$
$\Rightarrow a=\pm 3$
$\Rightarrow a=3(\because a=-3$ is not possible).