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

  • question_answer
    If \[\sin y=x\sin (a+y),\]then \[\frac{dy}{dx}=\] [Karnataka CET 2000; UPSEAT 2001; Pb. CET 2001; Kerala (Engg.) 2005]

    A)            \[\frac{{{\sin }^{2}}(a+y)}{\sin (a+2y)}\]

    B)            \[\frac{{{\sin }^{2}}(a+y)}{\sin (a+2y)}\]

    C)            \[\frac{{{\sin }^{2}}(a+y)}{\sin a}\]

    D)            \[\frac{{{\sin }^{2}}(a+y)}{\cos a}\]

    Correct Answer: C

    Solution :

               \[\sin y=x\sin (a+y)\]Þ\[x=\frac{\sin y}{\sin (a+y)}\]                    Þ  \[1=\frac{\cos y.\frac{dy}{dx}.\sin (a+y)-\sin y\cos (a+y)\frac{dy}{dx}}{{{\sin }^{2}}(a+y)}\]                            \[=\frac{\frac{dy}{dx}.\sin (a+y-y)}{{{\sin }^{2}}(a+y)}\Rightarrow \frac{dy}{dx}=\frac{{{\sin }^{2}}(a+y)}{\sin a}\].


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