JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    The value of \[\underset{x\to 0}{\mathop{\lim }}\,\frac{x\cos x-\log (1+x)}{{{x}^{2}}}\]is [RPET 1999]

    A)                 ½

    B)                 0

    C)                 1

    D)                 None of these

    Correct Answer: A

    Solution :

                       \[\underset{x\to 0}{\mathop{\lim }}\,\frac{x\cos x-\log (1+x)}{{{x}^{2}}}\],      \[\left( \frac{0}{0}\text{form} \right)\]            Applying L-Hospital?s rule, we have            \[\underset{x\to 0}{\mathop{\lim }}\,\,\frac{\cos x-x\sin x-\frac{1}{x+1}}{2x}\],    \[\left( \frac{0}{0}\text{form} \right)\]                                 \[=\underset{x\to 0}{\mathop{\lim }}\,\,\frac{-\sin x-\sin x-x\cos x+\frac{1}{{{(x+1)}^{2}}}}{2}=\frac{1}{2}\].


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