12th Class Mathematics Sample Paper Mathematics Olympiad - Sample Paper-1

  • question_answer
    If f(x) be a periodic function of period a, then \[\int\limits_{0}^{na}{\mathbf{f}\left( \mathbf{x} \right)}\]is equal to:

    A)  \[n.\int\limits_{0}^{n}{\mathbf{f}\left( \mathbf{x} \right)}.dx\]               

    B)  \[\int\limits_{0}^{a}{\mathbf{f}\left( \mathbf{x} \right)}.dx\]

    C)  \[(n+1)\int\limits_{0}^{a}{\mathbf{f}\left( \mathbf{x} \right)}.dx\]     

    D)  \[(n-1).\int\limits_{0}^{a}{\mathbf{f}\left( \mathbf{x} \right)}.dx\]

    Correct Answer: D

    Solution :

    [d]  \[\because I=\int\limits_{a}^{na}{f(x).dx}=\int\limits_{a}^{0}{f(x).dx}+\int\limits_{a}^{na}{f(x).dx}\] \[=-\int\limits_{a}^{a}{(x).dx}+\int\limits_{0}^{na}{f(x).dx}=-\int\limits_{0}^{a}{f(x).dx}+\int\limits_{0}^{a}{f(x).dx}\](By property of definite Integral) \[I=\left( n-1 \right).\int\limits_{a}^{a}{(x).dx}\] Hence option [d] is correct.


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