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

  • question_answer
    \[\int_{{}}^{{}}{\frac{\cos x-\sin x}{\sqrt{\sin 2x}}\ dx}\] equals [RPET 1996]

    A)            \[{{\cosh }^{-1}}(\sin x+\cos x)+c\]                                

    B)            \[{{\sinh }^{-1}}(\sin x+\cos x)+c\]

    C)            \[-{{\cosh }^{-1}}(\sin x+\cos x)+c\]

    D)   \[-{{\sinh }^{-1}}(\sin x+\cos x)+c\]

    Correct Answer: A

    Solution :

               \[I=\int_{{}}^{{}}{\frac{\cos x-\sin x}{\sqrt{\sin 2x}}}\,dx\]\[=\int_{{}}^{{}}{\frac{\cos x-\sin x}{\sqrt{{{(\sin x+\cos x)}^{2}}-1}}}\,dx\]            Put \[\sin x+\cos x=t\Rightarrow (\cos x-\sin x)\,dx=dt\]            \[I=\int_{{}}^{{}}{\frac{dt}{\sqrt{{{t}^{2}}-1}}}={{\cosh }^{-1}}t+c={{\cosh }^{-1}}(\sin x+\cos x)+c\].


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