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

  • question_answer
    If \[f(x)=\left\{ \begin{matrix}    {{x}^{n}}\sin (1/{{x}^{2}}),x\ne 0  \\    0,x=0  \\ \end{matrix} \right.\], \[(n\in I)\], then

    A) \[\underset{x\to 0}{\mathop{\lim }}\,f(x)\] exists for \[n>1\]

    B) \[\underset{x\to 0}{\mathop{\lim }}\,f(x)\] exists for \[n<0\]

    C) \[\underset{x\to 0}{\mathop{\lim }}\,f(x)\] Does not exist for any value of n

    D) \[\underset{x\to 0}{\mathop{\lim }}\,f(x)\] cannot be determined

    Correct Answer: A

    Solution :

    [a] for \[n>1,\] \[\underset{x\to 0}{\mathop{\lim }}\,{{x}^{n}}\sin (1/{{x}^{2}})=0x\] (any value between -1 and 1)=0 For n<0, \[\underset{x\to 0}{\mathop{\lim }}\,{{x}^{n}}\sin (1/{{x}^{2}})=\infty \times \] (any value between -1 and 1) = \[\infty \].


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