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

  • question_answer
    If then \[\frac{dy}{dx}=\] [DSSE 1980; CBSE 1980]

    A)            \[\frac{y[2xy-{{y}^{2}}\cos (xy)-1]}{x{{y}^{2}}\cos (xy)+{{y}^{2}}-x}\]

    B)            \[\frac{[2xy-{{y}^{2}}\cos (xy)-1]}{x{{y}^{2}}\cos (xy)+{{y}^{2}}-x}\]

    C)            \[-\frac{y[2xy-{{y}^{2}}\cos (xy)-1]}{x{{y}^{2}}\cos (xy)+{{y}^{2}}-x}\]

    D)            None of these

    Correct Answer: A

    Solution :

               \[\sin (xy)+\frac{x}{y}={{x}^{2}}-y\]            Differentiating both sides,            \[\cos (xy)\frac{d}{dx}(xy)+x\left\{ -\frac{1}{{{y}^{2}}} \right\}\frac{dy}{dx}+\frac{1}{y}=2x-\frac{dy}{dx}\]            Þ  \[[x\cos (xy)-\frac{x}{{{y}^{2}}}+1]\frac{dy}{dx}=2x-\frac{1}{y}-y\cos (xy)\]            Þ  \[\frac{dy}{dx}=\left[ \frac{2x{{y}^{2}}-y-{{y}^{3}}\cos (xy)}{x{{y}^{2}}\cos (xy)-x+{{y}^{2}}} \right]\].


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