JEE Main & Advanced Mathematics Definite Integration Question Bank Properties of Definite Integration

  • question_answer
    \[\int_{\,0}^{\,1000}{{{e}^{x-[x]}}dx}\] is                                              [AMU 2002]

    A)                 \[{{e}^{1000}}-1\]

    B)                 \[\frac{{{e}^{1000}}-1}{e-1}\]

    C)                 \[1000(e-1)\]    

    D)                 \[\frac{e-1}{1000}\]

    Correct Answer: C

    Solution :

               \[{{e}^{x-[x]}}\] is a periodic function with period 1.            \[\therefore \int_{0}^{1000}{{{e}^{x-[x]}}dx=1000\int_{0}^{1}{{{e}^{x-[x]}}dx}}\],  \[[\because [x]=0,\,\,\text{if}\,\,0<x<1]\]                                                             \[=1000\text{ }\,[{{e}^{x}}]_{0}^{1}\]\[=1000\,(e-1)\].


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