CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2007

  • question_answer
    If\[g(x)=\int_{0}^{x}{{{\cos }^{4}}}tdt,\]then\[g(x+\pi )\]is equal to

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

    B)  \[g(x)-g(\pi )\]

    C)  \[g(x).g(\pi )\] 

    D)         \[\frac{g(x)}{g(\pi )}\]

    E)  \[\frac{g(\pi )}{g(x)}\]

    Correct Answer: A

    Solution :

    \[\because \]\[g(x)=\int_{0}^{x}{{{\cos }^{4}}t\,dt}\] \[\therefore \]\[g(x+\pi )=\int_{0}^{\pi +x}{{{\cos }^{4}}t}\,dt\]                                 \[=\int_{0}^{\pi }{{{\cos }^{4}}t}\,dt+\int_{\pi }^{\pi +x}{{{\cos }^{4}}t}\,dt\]                                 \[={{I}_{1}}+{{I}_{2}}\] \[\Rightarrow \]               \[{{I}_{1}}=g(\pi )\]and\[{{I}_{2}}=\int_{\pi }^{\pi +x}{{{\cos }^{4}}t}\,dt\] \[\Rightarrow \]               \[{{I}_{2}}=\int_{0}^{x}{{{\cos }^{4}}(y+\pi )}\,dy\]                 \[=\int_{0}^{x}{{{[\cos (\pi +y)]}^{4}}}dy\]                 \[=\int_{0}^{x}{{{\cos }^{4}}y\,}dy=g(x)\]


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