JEE Main & Advanced Mathematics Differentiation Question Bank Self Evaluation Test - Limits and Derivatives

  • question_answer
    \[\underset{x\to 0}{\mathop{\lim }}\,\left[ \frac{\sin (sgn(x))}{(sgn(x))} \right],\] where [.] denotes the greatest integer function, is equal to

    A) 0

    B) 1

    C) -1

    D) Does not exist

    Correct Answer: A

    Solution :

    [a] \[=\underset{x\to 0+}{\mathop{\lim }}\,\left[ \frac{\sin (sgn)x}{\sgn (x)} \right]=\underset{x\to 0+}{\mathop{\lim }}\,\left[ \frac{\sin 1}{1} \right]=0\] \[=\underset{x\to {{0}^{-}}}{\mathop{\lim }}\,\left[ \frac{\sin (sgnx)}{\sgn (x)} \right]=\underset{x\to {{0}^{-}}}{\mathop{\lim }}\,\left[ \frac{\sin (-1)}{-1} \right]\] \[=\underset{x\to {{0}^{-}}}{\mathop{\lim }}\,[sin1]\] Hence, the given limit is 0.


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