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

  • question_answer
    \[\int_{{}}^{{}}{\frac{1}{x{{\cos }^{2}}(1+\log x)}\ dx=}\]

    A)            \[\tan \,(1+\log x)+c\]

    B)            \[\cot \,(1+\log x)+c\]

    C)            \[-\tan \,(1+\log x)+c\]

    D)            \[-\cot (\,1+\log x)+c\]

    Correct Answer: A

    Solution :

                       Put \[1+\log x=t\Rightarrow \frac{1}{x}\,dx=dt,\] then                    \[\int_{{}}^{{}}{\frac{1}{x{{\cos }^{2}}(1+\log x)}\,dx}=\int_{{}}^{{}}{\frac{dt}{{{\cos }^{2}}t}=\int_{{}}^{{}}{{{\sec }^{2}}t\,dt}}\]                                                                               \[=\tan t+c=\tan (1+\log x)+c.\]


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