JEE Main & Advanced Sample Paper JEE Main - Mock Test - 19

  • question_answer
    \[\underset{x\to \frac{{{\pi }^{-}}}{4}}{\mathop{\lim }}\,(i+\tan \,x)\left[ (1+\tan x){{\log }_{e}}\left( \frac{1+\tan x}{2+\tan x} \right)+1 \right]\]is equal to

    A) \[1/3\]               

    B)        \[1/2\]

    C) \[1\]                 

    D)        \[2\]

    Correct Answer: B

    Solution :

    [b] Let \[1\tan x=\frac{1}{t}\] \[\therefore \] Given limit \[=\underset{t\to {{0}^{+}}}{\mathop{\lim }}\,\frac{1}{t}\left( \frac{1}{t}.{{\log }_{e}}\left( \frac{1}{1+t} \right)+1 \right)\] \[=\underset{t\to {{0}^{+}}}{\mathop{\lim }}\,\frac{t-{{\log }_{e}}(1+t)}{{{t}^{2}}}\] \[=\underset{t\to {{0}^{+}}}{\mathop{\lim }}\,\frac{1-\frac{1}{1+t}}{2t}=\frac{1}{2}\]


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