JEE Main & Advanced Mathematics Differentiation Question Bank Differentiation of implicit function Parametric

  • question_answer
    If \[x=a\text{ }\left( \cos t+\log \tan \frac{t}{2} \right)\,,y=a\sin t,\]then \[\frac{dy}{dx}=\] [RPET 1997; MP PET 2001]

    A)            \[\tan t\]

    B)            \[-\tan t\]

    C)            \[\cot t\]

    D)            \[-\cot t\]

    Correct Answer: A

    Solution :

               Given that \[x=a\left( \cos t+\log \tan \frac{t}{2} \right)\] and \[y=a\sin t\]. Differentiating with respect to t, we get \[\frac{dy}{dt}=a\cos t\]                                                                         .....(i)            and \[\frac{dx}{dt}=a\left[ -\sin t+\cot \left( \frac{t}{2} \right)\,\left( \frac{1}{2} \right){{\sec }^{2}}\left( \frac{t}{2} \right) \right]\]                    \[=a\left( -\sin t+\frac{1}{\sin t} \right)=a\frac{{{\cos }^{2}}t}{\sin t}=a\cos t\cot t\]     .....(ii)            From (ii) and (i), we get \[\frac{dy}{dx}=\tan t\].


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