Find the value of \(k\), if the angle between the straight lines represented by \(2 x^2+5 x y+3 y^2+6 x+7…
Find the value of \(k\), if the angle between the straight lines represented by \(2 x^2+5 x y+3 y^2+6 x+7 y+4=0\) is \(\tan ^{-1}(k)\).
- \(\left(\frac{1}{5}\right)\) only
- \(\left(\frac{-1}{5}\right)\) only
- \(\pm \frac{1}{5}\)
- 0
Solution
Straight lines \(2 x^2+5 x y+3 y^2+6 x+7 y+4=0\)
Angle between straight lines represented by
\(\begin{aligned}
& a x^2+b y^2+2 g x+2 f y+c+2 h x y=0 \text { is } \\
& \tan \theta=\frac{2 \sqrt{h^2-a b}}{a+b}
\end{aligned}\)
\(\begin{aligned}
\tan \theta & =\frac{2 \sqrt{(5 / 2)^2-6}}{5}= \pm \frac{1}{5} \\
\Rightarrow \quad \theta & =\tan ^{-1} K=\tan ^{-1}\left( \pm \frac{1}{5}\right) \Rightarrow\left(K= \pm \frac{1}{5}\right)
\end{aligned}\)
Asked in: AP EAMCET 2020 (17 Sep Shift 1)
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