Q110 / 200 · Manipal (MET) 2010 · Mathematics
The locus of the point of intersection of tangents to the circle $x=a \cos \theta, y=a \sin \theta$ at the points, whose parametric angles differe by $\frac{\pi}{2}$, is
- Aa straight line
- Correct answerBa circle
- Ca pair of straight line
- DNone of the above
Solution
We have, the given circle $x=a \cos \theta, y=a \sin \theta$
$\Rightarrow x^2+y^2=a^2...(i)$
Tangents to the circle (i) at $\theta$ and $\left(\theta+\frac{\pi}{2}\right)$ are
$\begin{aligned} & x \cos \theta+y \sin \theta=a \\ & \text { and } x \cos \left(\theta+\frac{\pi}{2}\right)+y \sin \left(\theta+\frac{\pi}{2}\right)=a\end{aligned}$
or $x \cos \theta+y \sin \theta=a$
and $-x \sin \theta+y \cos \theta=a$
Squaring and adding, we get $x^2+y^2=2 a^2$
which is a circle.
Hence, the correct answer is option: 'B'.