Question

The polar equation of $x^2-y^2=2ax$ is

• A. $r\cos 2\theta =a\cos \theta$
• B. $r\cos 2\theta =a\sin \theta$
• C. $r\cos 2\theta =2a\cos \theta$
• D. $r\sin 2\theta =2a\cos \theta$

Answer 1

Answer: (C)

$r\cos 2\theta =2a\cos \theta$

put $x=r\cos \theta$ & $y=r\sin \theta$ in $x^2-y^2=2ax$
$r^2({\cos }^2\theta -{\sin }^2\theta )=2ar\cos \theta$
$\Rightarrow r\cos 2\theta =2a\cos \theta$
Ans: C