JEE Main & Advanced Mathematics Indefinite Integrals Question Bank Integration of Rational Function by Using Partial Fractions

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

    A)                 \[\frac{{{\cos }^{5}}x}{5}-\frac{{{\cos }^{3}}x}{3}+c\]

    B)                 \[\frac{{{\cos }^{5}}x}{5}+\frac{{{\cos }^{3}}x}{3}+c\]

    C)                 \[\frac{{{\sin }^{5}}x}{5}-\frac{{{\sin }^{3}}x}{3}+c\]

    D)                 \[\frac{{{\sin }^{5}}x}{5}+\frac{{{\sin }^{3}}x}{3}+c\]

    Correct Answer: A

    Solution :

                       \[\int_{{}}^{{}}{{{\sin }^{3}}x{{\cos }^{2}}x\,dx}=\int_{{}}^{{}}{(1-{{\cos }^{2}}x){{\cos }^{2}}x\,.\,\sin x\,dx}\]                    Put \[\cos x=t\Rightarrow -\sin x\,dx=dt,\] then it reduces to                 \[-\int_{{}}^{{}}{({{t}^{2}}-{{t}^{4}})dt}=\frac{{{t}^{5}}}{5}-\frac{{{t}^{3}}}{3}+c=\frac{{{(\cos x)}^{5}}}{5}-\frac{{{(\cos x)}^{3}}}{3}+c\].


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