JEE Main & Advanced Mathematics Indefinite Integrals Question Bank Mock Test - Integrals

  • question_answer
    If \[\int_{0}^{1}{{{\cot }^{-1}}(1-x+{{x}^{2}})dx=\lambda \int_{0}^{1}{{{\tan }^{-1}}xdx,}}\] then \[\lambda \] is equal to

    A) 1                     

    B) 2

    C) 3         

    D) 4

    Correct Answer: B

    Solution :

    [b] \[\int_{0}^{1}{{{\cot }^{-1}}(1-x+{{x}^{2}})dx}\] \[=\int_{0}^{1}{{{\tan }^{-1}}\left( \frac{1}{1-x+{{x}^{2}}} \right)}dx\] \[=\int_{0}^{1}{{{\tan }^{-1}}\left( \frac{x+(1-x)}{1-x(1-x)} \right)}dx\] \[=\int_{0}^{1}{{{\tan }^{-1}}xdx+\int_{0}^{1}{{{\tan }^{-1}}(1-x)dx}}\] \[=\int_{0}^{1}{{{\tan }^{-1}}xdx+\int_{0}^{1}{{{\tan }^{-1}}[1-(1-x)]dx}}\] \[=2\int_{0}^{1}{{{\tan }^{-1}}xdx}\]or \[\lambda =2\]


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