JEE Main & Advanced Mathematics Pair of Straight Lines Question Bank Angle between the pair of straight lines, Condition for parallel and perpendicular lines

  • question_answer
    The angle between the lines represented by the equation \[({{x}^{2}}+{{y}^{2}})\sin \theta +2xy=0\]is

    A)            \[\theta \]                             

    B)            \[\frac{\theta }{2}\]

    C)            \[\frac{\pi }{2}-\theta \]  

    D)            \[\frac{\pi }{2}-\frac{\theta }{2}\]

    Correct Answer: C

    Solution :

               \[\theta ={{\tan }^{-1}}\left( \frac{2\sqrt{1-{{\sin }^{2}}\theta }}{2\sin \theta } \right)={{\tan }^{-1}}\left( \frac{\cos \theta }{\sin \theta } \right)\]            \[{{\tan }^{-1}}\left\{ \tan \left( \frac{\pi }{2}-\theta  \right) \right\}=\frac{\pi }{2}-\theta \] .


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