JEE Main & Advanced Mathematics Applications of Derivatives Question Bank Tangent and Normal

  • question_answer
    The angle between curves \[{{y}^{2}}=4x\] and \[{{x}^{2}}+{{y}^{2}}=5\]at              (1, 2)  is                                             [Karnataka CET 1999]

    A)            \[{{\tan }^{-1}}(3)\]

    B)            \[{{\tan }^{-1}}(2)\]

    C)            \[\frac{\pi }{2}\]

    D)            \[\frac{\pi }{4}\]

    Correct Answer: A

    Solution :

               For curve \[{{y}^{2}}=4x\] Þ \[\frac{dy}{dx}=\frac{4}{2y}\]                    \\[{{\left( \frac{dy}{dx} \right)}_{(1,\,2)}}=1\] and for curve \[{{x}^{2}}+{{y}^{2}}=5\] Þ \[\frac{dy}{dx}=\frac{-x}{y}\]            \ \[{{\left( \frac{dy}{dx} \right)}_{(1,\,2)}}=\frac{-1}{2}\]            \ Angle between the curves is            \[\theta ={{\tan }^{-1}}\left| \,\frac{\frac{-1}{2}\,-1}{1+\left( \frac{-1}{2} \right)}\, \right|={{\tan }^{-1}}(3)\].


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