JEE Main & Advanced Mathematics Indefinite Integrals Question Bank Fundamental Integration

  • question_answer
    \[\int_{{}}^{{}}{\frac{1-\tan x}{1+\tan x}\ dx=}\] [MP PET 1994]

    A)            \[\log \sec \left( \frac{\pi }{4}-x \right)+c\]

    B)            \[\log \cos \left( \frac{\pi }{4}+x \right)+c\]

    C)            \[\log \sin \left( \frac{\pi }{4}+x \right)+c\]

    D)            None of these

    Correct Answer: C

    Solution :

               \[\int_{{}}^{{}}{\frac{1-\tan x}{1+\tan x}\,dx}=\int_{{}}^{{}}{\tan \left( \frac{\pi }{4}-x \right)}\,dx\]                    \[=\int_{{}}^{{}}{\frac{\sin \left( \frac{\pi }{4}-x \right)}{\cos \left( \frac{\pi }{4}-x \right)}}\,dx=\log \cos \left( \frac{\pi }{4}-x \right)+c\]                    \[=\log \sin \left( \frac{\pi }{4}+x \right)+c\].


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