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

  • question_answer
    The limit \[\underset{x\to 0}{\mathop{\lim }}\,{{(cosx)}^{1/\sin x\frac{1}{\sin x}}}\] is equal to

    A) \[e\]

    B) \[{{e}^{-1}}\]

    C) 1

    D) Does not exist

    Correct Answer: C

    Solution :

    [c] \[\underset{x\to 0}{\mathop{\lim }}\,{{(cos)}^{\frac{1}{\sin x}}}\] is \[{{1}^{\infty }}\] form \[={{e}^{\underset{x\to \infty }{\mathop{Lim}}\,(cosx-1)\frac{1}{\sin x}}}\] \[={{e}^{\underset{x\to 0}{\mathop{Lim}}\,\frac{-2{{\sin }^{2}}x/2}{2{{\sin }^{x}}/{{2}^{\cos x}}/2}}}={{e}^{\underset{x\to 0}{\mathop{Lim}}\,\left( -\tan \frac{x}{2} \right)}}={{e}^{o}}=1\]


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