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

  • question_answer
    \[\int_{{}}^{{}}{\frac{1}{x\sqrt{1+\log x}}\ dx=}\]           [Roorkee 1977]

    A)            \[\frac{2}{3}{{(1+\log x)}^{3/2}}+c\]

    B)            \[{{(1+\log x)}^{3/2}}+c\]

    C)            \[2\sqrt{1+\log x}+c\]

    D)            \[\sqrt{1+\log x}+c\]

    Correct Answer: C

    Solution :

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


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