RAJASTHAN ­ PET Rajasthan PET Solved Paper-2005

  • question_answer
    The value of\[\int{{{x}^{2}}{{e}^{{{x}^{3}}}}}\cos ({{e}^{{{x}^{3}}}})dx\] is

    A)  \[\sin ({{e}^{{{x}^{3}}}})+c\]

    B)  \[\frac{1}{3}\sin ({{e}^{{{x}^{3}}}})+c\]

    C)  \[-\frac{1}{3}\sin ({{e}^{{{x}^{3}}}})+c\]

    D)  \[3\sin ({{e}^{{{x}^{3}}}})+c\]

    Correct Answer: B

    Solution :

     Let \[I=\int{{{x}^{2}}{{e}^{2}}}\cos ({{e}^{{{x}^{3}}}})dx\] Put \[{{e}^{{{x}^{3}}}}=t\] \[\Rightarrow \] \[{{e}^{{{x}^{3}}}}.3{{x}^{2}}dx=dt\] \[\Rightarrow \] \[{{x}^{2}}{{e}^{2}}dx=\frac{1}{3}dt\] \[\therefore \] \[I=\int{\frac{1}{3}\cos t\,dt}\] \[=\frac{\sin t}{3}+c\] \[=\frac{\sin ({{e}^{{{x}^{3}}}})}{3}+c\]


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