CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2000

  • question_answer
    \[\int{\frac{{{e}^{x}}(1+x)}{{{\cos }^{2}}(x{{e}^{x}})}dx}\]is equal to:

    A)  \[2\log \cos (x{{e}^{x}})+c\]

    B)  \[\sec (x{{e}^{x}})+c\]

    C)  \[\tan (x{{e}^{x}})+c\]

    D)  \[\tan (x+{{e}^{x}})+c\]

    E)  \[{{e}^{x}}\tan (x{{e}^{x}})+c\]

    Correct Answer: C

    Solution :

    Let \[I=\int{\frac{{{e}^{x}}(1+x)}{{{\cos }^{2}}(x{{e}^{x}})}}dx\] Put         \[x{{e}^{x}}=t\] \[\Rightarrow \]               \[(x{{e}^{x}}+{{e}^{x}})dx=dt\] \[\Rightarrow \]               \[{{e}^{x}}(x+1)dx=dt\] \[\therefore \]  \[I=\int{\frac{dt}{{{\cos }^{2}}t}}=\int{{{\sec }^{2}}t\,dt}\]                 \[=\tan t+c\]                 \[=\tan (x{{e}^{x}})+c\]


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