JEE Main & Advanced JEE Main Paper (Held On 11-Jan-2019 Morning)

  • question_answer
    The value of the integral\[\int\limits_{-2}^{2}{\frac{{{\sin }^{2}}x}{\left[ \frac{x}{\pi } \right]+\frac{1}{2}}}dx\](where [x] denotes the greatest integer less than or equal to x) is [JEE Main Online Paper (Held On 11-Jan-2019 Morning]

    A) 0                                             

    B)               sin 4

    C)               4                                             

    D)               \[4-sin\text{ }4\]

    Correct Answer: A

    Solution :

    Let \[I=\int\limits_{-2}^{2}{\frac{{{\sin }^{2}}x}{\left[ \frac{x}{\pi } \right]+\frac{1}{2}}}dx\] \[\Rightarrow \]\[I=\int\limits_{0}^{2}{\left( \frac{{{\sin }^{2}}x}{\left[ \frac{x}{\pi } \right]+\frac{1}{2}}+\frac{{{\sin }^{2}}(-x)}{\left[ -\frac{x}{\pi } \right]+\frac{1}{2}} \right)}dx\] \[\left( \left[ \frac{x}{\pi } \right]+\left[ -\frac{x}{\pi } \right]=-1\,as\,x\ne n\pi  \right)\] \[\Rightarrow \]\[I=\int\limits_{0}^{2}{\left( \frac{{{\sin }^{2}}x}{\left[ \frac{x}{\pi } \right]+\frac{1}{2}}+\frac{{{\sin }^{2}}x}{-1-\left[ \frac{x}{\pi } \right]+\frac{1}{2}} \right)}dx=0\]


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