JCECE Engineering JCECE Engineering Solved Paper-2003

  • question_answer
    Let\[f(x)=x-[x]\]for all real number, where\[[x]\]is the integral part of\[x\], then\[\int_{-1}^{1}{f(x)}dx\]is equal to:

    A) \[1\]                                     

    B) \[2\]

    C) \[0\]                                     

    D)  \[1/2\]

    Correct Answer: A

    Solution :

    Given,   \[f(x)=x-[x]\] \[\therefore \]  \[\int_{-1}^{1}{f(x)}dx=\int_{-1}^{1}{(x-[x])dx}\]                 \[=\int_{-1}^{0}{(x-[x])dx+\int_{0}^{1}{(x-[x])dx}}\]                 \[=\int_{-1}^{0}{(x+1)dx+\int_{1}^{0}{x}\,\,dx}\]                 \[=\left[ \frac{{{x}^{2}}}{2}+x \right]_{-1}^{0}+\left[ \frac{{{x}^{2}}}{2} \right]_{0}^{1}\]                 \[=\left[ 0-\frac{1}{2}+1 \right]+\left[ \frac{1}{2}-0 \right]\]                 \[=\frac{1}{2}+\frac{1}{2}=1\] Note: For every real value of x, the value of \[[x]\] is always an integers.


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