JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    The value of \[\underset{x\to 0}{\mathop{\lim }}\,\frac{\log [1+{{x}^{3}}]}{{{\sin }^{3}}x}=\] [AMU 2005]

    A)                 0

    B)             1

    C)                 3

    D)                 None of these

    Correct Answer: B

    Solution :

     \[\underset{x\to 0}{\mathop{\lim }}\,\frac{\log (1+{{x}^{3}})}{{{\sin }^{3}}x}\]\[=\underset{x\to 0}{\mathop{\lim }}\,\frac{3{{x}^{2}}/(1+{{x}^{3}})}{3{{\sin }^{2}}x\cos x}\]                                                                 [By using L- Hospital rule]                                             \[=\underset{x\to 0}{\mathop{\lim }}\,\left[ \frac{1}{1+{{x}^{3}}}{{\left( \frac{x}{\sin x} \right)}^{2}}.\frac{1}{\cos x} \right]\]\[=\frac{1}{1+0}.{{(1)}^{2}}.\frac{1}{1}=1\].


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