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

  • question_answer
    \[\int_{{}}^{{}}{{{\sin }^{3}}x\ dx}\] is equal to [SCRA 1996]

    A)            \[{{\sin }^{2}}x+1\]

    B)            \[\sin {{x}^{2}}+{{x}^{2}}+1\]

    C)            \[\frac{{{\cos }^{3}}x}{3}-\cos x\]

    D)            \[\frac{1}{4}{{\sin }^{4}}x-\frac{3}{4}{{\sin }^{2}}x\]

    Correct Answer: C

    Solution :

                       \[\int_{{}}^{{}}{{{\sin }^{3}}x\,dx}=\int_{{}}^{{}}{{{\sin }^{2}}x\,.\,\sin x\,dx}\]            \[=\int_{{}}^{{}}{\sin x(1-{{\cos }^{2}}x)\,dx}\] \[=\int_{{}}^{{}}{\sin x\,dx}-\int_{{}}^{{}}{{{\cos }^{2}}x\,.\,\sin x\,dx}\]\[=-\cos x+\frac{{{\cos }^{3}}x}{3}\].


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