JEE Main & Advanced Mathematics Functions Question Bank Continuity

  • question_answer
    If \[f(x)=\left\{ \begin{align}   & {{x}^{2}}\sin \frac{1}{x},\ \ \ \text{when }x\ne 0 \\  & \,\,\,\,\,\,\,\,\,\,\,\,\,\,0,\,\,\,\,\text{when}\,x=0 \\ \end{align} \right.\], then

    A)            \[f(0+0)=1\]

    B)            \[f(0-0)=1\]

    C)            f is continuous at\[x=0\]

    D)            None of these

    Correct Answer: C

    Solution :

               \[\underset{x\to {{0}^{+}}}{\mathop{\lim }}\,\,f(x)={{x}^{2}}\sin \frac{1}{x},\] but \[-1\le \sin \frac{1}{x}\le 1\] and \[x\to 0\]                    Therefore, \[\underset{x\to {{0}^{+}}}{\mathop{\lim }}\,\,f(x)=0=\underset{x\to {{0}^{-}}}{\mathop{\lim }}\,\,f(x)=f(0)\]            Hence \[f(x)\] is continuous at \[x=0.\]


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