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

  • question_answer
    If \[g(x)=\int_{0}^{x}{{{\cos }^{4}}t\,dt,}\] then \[g(x+\pi )\] equals [IIT 1997 Re-Exam; DCE 2001; UPSEAT 2001; Pb. CET 2002]

    A)                 \[g(x)+g(\pi )\] 

    B)                 \[g(x)-g(\pi )\]

    C)                 \[g(x)g(\pi )\]   

    D)                 \[g(x)/g(\pi )\]

    Correct Answer: A

    Solution :

               \[g(x+\pi )=\int_{0}^{x+\pi }{{{\cos }^{4}}t\,dt=\int_{0}^{\pi }{{{\cos }^{4}}t\,dt+\int_{\pi }^{x+\pi }{{{\cos }^{4}}t\,dt}}}\]                                  \[=g(\pi )+f(x)\]                    \[f(x)=\int_{0}^{x}{{{\cos }^{4}}u\,du=g(x)}\],  \[(\because t=\pi +u)\]                                 \[\therefore \,\,g(x+\pi )=g(x)+g(\pi )\].


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