JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    If \[f(x)=\left\{ \begin{align}   & x\sin \frac{1}{x},\ \ \ \ \ x\ne 0 \\  & \ \ \ \ \ \ 0,\ \ \ \ \ x=0 \\ \end{align} \right.\],  then \[\underset{x\to 0}{\mathop{\lim }}\,f(x)=\]                 [IIT 1988; MNR 1988; SCRA 1996; UPSEAT 2000, 01]

    A)                 1

    B)                 0

    C)                 ?1

    D)                 None of these

    Correct Answer: B

    Solution :

                       Here \[f(0)=0\]            Since \[-1\le \sin \frac{1}{x}\le 1\,\,\Rightarrow \,\,-|\,\,x\,\,|\,\,\le x\sin \frac{1}{x}\le \,\,|\,\,x\,\,|\]            We know that \[\underset{x\to 0}{\mathop{\lim }}\,\,\,|\,\,x\,\,|\,=0\] and \[\underset{x\to 0}{\mathop{\lim }}\,\,\,|\,\,x\,\,|\,=0\]                 In this way \[\underset{x\to 0}{\mathop{\lim }}\,\,\,f(x)=0.\]


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