BCECE Engineering BCECE Engineering Solved Paper-2002

  • question_answer
    \[\int_{1}^{2}{\log x\,dx}\]is equal to:

    A) \[\log \left( \frac{e}{2} \right)\]

    B)         \[\log \left( \frac{2}{e} \right)\]               

    C)         \[\log \left( \frac{e}{4} \right)\]               

    D)         \[\log \left( \frac{4}{e} \right)\]

    Correct Answer: D

    Solution :

    Let \[I=\int_{1}^{2}{1.\log x\,dx}\] \[=[x\log x-\int_{{}}^{{}}{1\,dx}]_{1}^{2}\] \[=[x\log x-x]_{1}^{2}\] \[=2\log 2-2-(0-1)\] \[=2\log 2-1={{\log }_{e}}{{2}^{2}}-{{\log }_{e}}e\] \[=\log \left( \frac{4}{e} \right)\]


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