CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2004

  • question_answer
      If\[f(x)=\sin (\log x)\]and \[y=f\left( \frac{2x+3}{3-2x} \right),\] then \[\frac{dy}{dx}\]at\[x=1\]is equal to:

    A)  6 sin log (5)

    B)  5 sin log (6)

    C)  12 sin log (5)

    D)  5 sin log (12)

    E)  12 sin log (6)

    Correct Answer: C

    Solution :

    \[\frac{dy}{dx}=f\left( \frac{2x+3}{3-2x} \right)\frac{d}{dx}\left( \frac{2x+3}{3-2x} \right)\] \[=\sin \log \left( \frac{2x+3}{3-2x} \right)\left( \frac{(3-2x)(2)-(2x+3)(-2)}{{{(3-2x)}^{2}}} \right)\] \[=\frac{12}{{{(3-2x)}^{2}}}\sin \left\{ \log \left( \frac{2x+3}{3-2x} \right) \right\}\] \[\therefore \] \[{{\left( \frac{dy}{dx} \right)}_{x=1}}=\frac{12}{{{(3-2)}^{2}}}.\sin \,\log 5\]


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