JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    \[\underset{x\to 0}{\mathop{\lim }}\,\sin \left( \frac{1}{x} \right)\] is [SCRA 1996]

    A)                 0

    B)                 1

    C)                 ?1

    D)                 Does not exist

    Correct Answer: D

    Solution :

                       \[\underset{x\to {{0}^{-}}}{\mathop{\lim }}\,f(x)=\underset{h\to 0}{\mathop{\lim }}\,f(0-h)\]                      \[=\underset{h\to 0}{\mathop{\lim }}\,\,\sin \,\left( \frac{-1}{h} \right)=\underset{h\to 0}{\mathop{\lim }}\,\,\,-\sin \frac{1}{h}\]                       = ? 1 (finite number lies between ? 1 to 1)            \[\underset{x\to {{0}^{+}}}{\mathop{\lim }}\,f(x)=\underset{h\to 0}{\mathop{\lim }}\,f(0+h)\]                   \[=\underset{h\to 0}{\mathop{\lim }}\,\,\,\sin \left( \frac{1}{h} \right)\]= (finite number lies between 0 to 1)                 \[\because \,\,\,\,\underset{x\to {{0}^{-}}}{\mathop{\lim }}\,f(x)\ne \underset{x\to {{0}^{+}}}{\mathop{\lim }}\,f(x)\];  \\[\underset{x\to 0}{\mathop{\lim }}\,\sin \left( \frac{1}{x} \right)\] does not exist.


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