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

  • question_answer
    If \[m,\,\,\,n\in {{I}_{0}}\] and \[\underset{x\to 0}{\mathop{\lim }}\,\frac{\tan 2x-n\sin x}{{{x}^{3}}}=\] some integer, then value of this limit is

    A) 3

    B) 2

    C) \[\frac{16+n}{12}\]

    D) None of these

    Correct Answer: A

    Solution :

    [a] \[\underset{x\to 0}{\mathop{\lim }}\,\frac{\tan 2x-n\sin x}{{{x}^{3}}}=I\] \[=\underset{x\to 0}{\mathop{\lim }}\,\frac{2x+\frac{8{{x}^{3}}}{3!}...-nx+\frac{n{{x}^{3}}}{3!}}{{{x}^{3}}}=I\] \[=\underset{x\to 0}{\mathop{\lim }}\,\frac{(2-n)x+\left( \frac{16+n}{6} \right){{x}^{3}}+....}{{{x}^{3}}}=I\] \[\Rightarrow n=2\] and, thus required value \[=\frac{16+n}{6}=3.\]


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