JEE Main & Advanced Sample Paper JEE Main - Mock Test - 40

  • question_answer
    Let \[f(x)={{(sex\,x)}^{\cos ec\,\,x}}+{{(\cot \,x)}^{\sin x}}.\]Then the value of \[\underset{x\to {{0}^{+}}}{\mathop{\lim }}\,f(x)\] is equal to

    A) \[-1\]

    B)                    \[0\]

    C) \[1\]

    D)        \[2\]

    Correct Answer: D

    Solution :

    [d] \[{{L}_{1}}=\underset{x\to 0}{\mathop{\lim }}\,\,\,{{(\sec x)}^{\cos ec\,x}}\]   (\[{{1}^{\infty }}\]form) \[={{e}^{\underset{x\to 0}{\mathop{\lim }}\,\,\,\cos ecx\,(\sec \,x-1)}}={{e}^{\underset{x\to 0}{\mathop{\lim }}\,\,\,\frac{1-\cos x}{\sin 2x}}}={{e}^{0}}=1\] \[{{L}_{2}}=\underset{x\to 0}{\mathop{\lim }}\,\,\,{{(cot\,x)}^{\sin x}}\] (\[{{\infty }^{0}}\] form) \[\therefore \,\,\,\,\,\,\,\,{{\log }_{e}}{{L}_{2}}=\underset{x\to 0}{\mathop{\lim }}\,\,\,(\sin \,\,x).{{\log }_{e}}(\cot x)\] \[=\underset{x\to 0}{\mathop{\lim }}\,\frac{{{\log }_{e}}(\cot x)}{\cos ec\,x}\] \[=\underset{x\to 0}{\mathop{\lim }}\,\frac{\cos e{{c}^{2}}x}{\cot x}\frac{1}{\cos ec\,x\,\,\cot x}\] \[=\underset{x\to 0}{\mathop{\lim }}\,\,\,\frac{\sin x}{{{\cos }^{2}}x}=0\] \[\therefore \,\,\,\,\,\,\,\,\,\,{{L}_{2}}={{e}^{0}}=1\] So,  \[{{L}_{2}}+{{L}_{2}}=1+1=2\]


You need to login to perform this action.
You will be redirected in 3 sec spinner