JEE Main & Advanced Mathematics Pair of Straight Lines Question Bank Equation of Pair of Straight Lines

  • question_answer
    The equation of one of the line represented by the equation \[{{x}^{2}}+2xy\cot \theta -{{y}^{2}}=0\], is

    A)            \[x-y\cot \theta =0\]

    B)            \[x+y\tan \theta =0\]

    C)            \[x\sin \theta +y(\cos \theta +1)=0\]

    D)            \[x\cos \theta +y(\sin \theta +1)=0\]

    Correct Answer: C

    Solution :

               The lines represented by the equation \[{{x}^{2}}+2xy\cot \theta -{{y}^{2}}=0\]are \[ax+hy\pm y\sqrt{{{h}^{2}}-ab}=0\]                    \[\Rightarrow x+y\cot \theta \pm y\sqrt{{{\cot }^{2}}\theta +1}=0\]                    \[\Rightarrow x+y\left( \frac{\cos \theta }{\sin \theta }\pm \frac{1}{\sin \theta } \right)=0\]\[\Rightarrow x\sin \theta +y(\cos \theta \pm 1)=0\]                    Hence, one line is \[x\sin \theta +y(\cos \theta +1)=0\] .


You need to login to perform this action.
You will be redirected in 3 sec spinner