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

  • question_answer
    \[\int{\text{cose}{{\text{c}}^{4}}x\,dx}=\]          [RPET 2002]

    A)            \[\cot x+\frac{{{\cot }^{3}}x}{3}+c\]

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

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

    D)   \[-\tan x-\frac{{{\tan }^{3}}x}{3}+c\]

    Correct Answer: C

    Solution :

                       \[=-\log ({{\cos }^{-1}}x)+c.\]\[=\int{\text{cose}{{\text{c}}^{2}}x}.\,\text{cose}{{\text{c}}^{2}}xdx\]                      \[=\int{\text{cose}{{\text{c}}^{2}}x(1+{{\cot }^{2}}x)\,dx}\]              \[=\int{\text{cose}{{\text{c}}^{2}}x\,\,dx}\,\,+\int{{{\cot }^{2}}x.\,\text{cose}{{\text{c}}^{2}}x\,dx}\]              \[=-\cot x-\frac{{{\cot }^{3}}x}{3}+c\].


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