KVPY Sample Paper KVPY Stream-SX Model Paper-29

  • question_answer
    The value of \[\int\limits_{{\scriptstyle{}^{-\pi }/{}_{2}}}^{{\scriptstyle{}^{\pi }/{}_{2}}}{\frac{dx}{[x]+[sinx]+4},}\] where \[[t]\] denotes the greatest integer less than or equal to \[t,\] is:

    A) \[\frac{1}{12}(7\pi +5)\]

    B) \[\frac{1}{12}(7\pi -5)\]

    C) \[\frac{3}{20}(4\pi -3)\]

    D) \[\frac{3}{10}(4\pi -3)\]

    Correct Answer: C

    Solution :

    \[\int\limits_{-\pi /2}^{\pi /2}{\frac{dx}{[x]+[sinx]+4}}\]
    \[=\int\limits_{-\pi /2}^{0}{\frac{dx}{[x]+-1+4}+}\int\limits_{0}^{\pi /2}{\frac{dx}{[x]+4}}\]
    \[=\int\limits_{-\pi /2}^{-1}{\frac{dx}{-2-1+4}+}\int\limits_{-1}^{0}{\frac{dx}{-1-1+4}}+\int\limits_{0}^{1}{\frac{dx}{4}+\int\limits_{1}^{\pi /2}{\frac{dx}{1+4}}}\]
    \[=-1+\frac{\pi }{2}+2+\frac{1}{4}+\frac{1}{5}\left( \frac{\pi }{2}-1 \right)\]
    \[=3\frac{\pi }{5}-\frac{9}{20}.\]


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