JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2013

  • question_answer
        If\[\int_{1/2}^{2}{\frac{1}{x}}\cos e{{c}^{101}}\left( x-\frac{1}{x} \right)dx=k,\]then the value of \[k\]is

    A)  1                            

    B)  \[\frac{1}{2}\]      

    C)  0                            

    D)  \[\frac{1}{101}\]

    Correct Answer: C

    Solution :

                    Let\[I=\int_{1/2}^{2}{\frac{1}{x}\cos e{{c}^{101}}\left( x-\frac{1}{x} \right)}dx\] put        \[x=\frac{1}{t}\] \[\Rightarrow \]               \[I=\int_{2}^{1/2}{t.\cos e{{c}^{101}}\left( \frac{1}{t}-t \right)\left( \frac{1}{{{t}^{2}}} \right)}dt\]                 \[=-\int_{2}^{1/2}{\frac{1}{t}\cos e{{c}^{101}}\left( t-\frac{1}{t} \right)}dt\] \[\Rightarrow \]               \[I=-I\] \[\Rightarrow \]               \[2I=0\] \[\therefore \]  \[I=0\]


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