JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    \[\underset{x\to 0}{\mathop{\lim }}\,{{\left( \frac{1+\tan x}{1+\sin x} \right)}^{\text{cosec }x}}\]is equal to [Kerala (Engg.) 2005] 

    A)                 \[e\]

    B)                 \[\frac{1}{e}\]

    C)                 1

    D)                 None of these

    Correct Answer: C

    Solution :

                       Given limit \[=\underset{x\to 0}{\mathop{\lim }}\,[{{(1+\tan x)}^{\cos ec\,x}}\times 1/{{(1+\sin x)}^{\cos ec\,x}}]\]            \[=\underset{x\to 0}{\mathop{\lim }}\,\,{{[{{\{1+\tan x)}^{\cot \,x}}\}}^{sec\,x}}\times \{1/{{(1+\sin x)}^{\cos ec\,x}}\}]\]                 \[={{e}^{\sec \,\,0}}.\frac{1}{e}=e\,.\,\frac{1}{e}=1.\]


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