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

  • question_answer
    If \[x=a\left( t-\frac{1}{t} \right)\,,y=a\] \[\left( t+\frac{1}{t} \right)\]then \[\frac{dy}{dx}=\] [Karnataka CET 2004]

    A)            \[\frac{y}{x}\]

    B)            \[\frac{-y}{x}\]

    C)            \[\frac{x}{y}\]

    D)            \[\frac{-x}{y}\]

    Correct Answer: C

    Solution :

               \[x=a\left( t-\frac{1}{t} \right)\] ....(i)  and  \[y=a\left( t+\frac{1}{t} \right)\]     .....(ii)                    Squaring (i) and (ii), then subtracting we get,                    \[{{x}^{2}}-{{y}^{2}}={{a}^{2}}(-4)\] or \[{{y}^{2}}-{{x}^{2}}=4{{a}^{2}}\]                    Differentiating both sides w.r.t. x,                    \[2y\frac{dy}{dx}-2x=0\]Þ \[\frac{dy}{dx}=\frac{x}{y}\].


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