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

  • question_answer
    If \[x=a(t+\sin t)\]and \[y=a(1-\cos t)\], then \[\frac{dy}{dx}\] equals  [RPET 1996; MP PET 2002]

    A)            \[\tan (t/2)\]

    B)            \[\cot (t/2)\]

    C)            \[\tan 2t\]

    D)            \[\tan t\]

    Correct Answer: A

    Solution :

               \[\frac{dy}{dx}=\frac{dy/dt}{dx/dt}=\frac{\frac{d}{dt}[a(1-\cos t)]}{\frac{d}{dt}[a(t+\sin t)]}\]                    \[\frac{dy}{dx}=\frac{a\sin t}{a+a\cos t}=\frac{\sin t}{1+\cos t}=\frac{2\sin \frac{t}{2}\cos \frac{t}{2}}{2{{\cos }^{2}}\frac{t}{2}}\]                    \[\therefore \frac{dy}{dx}=\tan \frac{t}{2}\].


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