Q89 / 160 · AP EAMCET 2021 (25 Aug Shift 1) · Mathematics
The angle between the lines $a b\left(x^2-y^2\right)+\left(a^2-b^2\right) x y=0$ is
- Correct answerA$\frac{\pi}{2}$
- B$\frac{\pi}{3}$
- C$\frac{\pi}{4}$
- D$\frac{\pi}{6}$
Solution
We have,
$$
\begin{aligned}
& a b\left(x^2-y^2\right)+\left(a^2-b^2\right) x y=0 \\
& a b x^2+\left(a^2-b^2\right) x y-a b y^2=0
\end{aligned}
$$
Sum of the coefficient of $x^2$ and $y^2$
$$
\text { i.e. } a b-a b=0
$$
$\therefore \quad$ Lines are perpendicular to each other.
$\therefore \quad$ Angle between lines $=\pi / 2$
Hence, the correct answer is option: 'A'.