JEE Main & Advanced Mathematics Indefinite Integrals Question Bank Integration by Substitution

  • question_answer
    \[\int_{{}}^{{}}{2x{{\cos }^{3}}{{x}^{2}}\sin {{x}^{2}}dx=}\]

    A)            \[-\frac{1}{4}{{\cos }^{4}}{{x}^{2}}+c\]

    B)            \[\frac{1}{4}{{\cos }^{4}}{{x}^{2}}+c\]

    C)            \[{{\cos }^{4}}{{x}^{2}}+c\]

    D)            None of these

    Correct Answer: A

    Solution :

                       Put \[t=\cos {{x}^{2}}\Rightarrow dt=-2x\sin {{x}^{2}}dx,\] then            \[\int_{{}}^{{}}{2x{{\cos }^{3}}{{x}^{2}}\sin {{x}^{2}}dx}=-\int_{{}}^{{}}{{{t}^{3}}dt}=-\frac{{{t}^{4}}}{4}+c\]                                                                       \[=-\frac{1}{4}{{\cos }^{4}}{{x}^{2}}+c.\]


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