JEE Main & Advanced Sample Paper JEE Main Sample Paper-2

  • question_answer
    The area bounded by the curve \[y=\left[ \frac{3}{{{x}^{2}}+1} \right],\,([.]\] denotes greatest integer function), on positive side of \[x\]-axis is

    A)  \[3\sqrt{2}\]                     

    B)  \[\frac{3}{\sqrt{2}}\]

    C)  \[\frac{3}{\sqrt{2}}-1\]                

    D)  infinite

    Correct Answer: B

    Solution :

    \[y=\left[ \frac{3}{{{x}^{2}}}+1 \right]=\left\{ \begin{matrix}    0, & x\in \left( \sqrt{2},\,\infty  \right)  \\    \begin{align}   & 1, \\  & 2, \\  & 3, \\ \end{align} & \begin{align}   & x\in \left( \frac{1}{\sqrt{2}},\,\sqrt{2} \right) \\  & x\in \left( 0,\,\frac{1}{\sqrt{2}} \right) \\  & x=0 \\ \end{align}  \\ \end{matrix} \right.\] \[\int\limits_{0}^{1/\sqrt{2}}{2dx+\int\limits_{1/\sqrt{2}}^{\sqrt{2}}{1dx=\sqrt{2}+\sqrt{2}-\frac{1}{\sqrt{2}}=\frac{3}{\sqrt{2}}}}\]


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