VIT Engineering VIT Engineering Solved Paper-2007

  • question_answer
    The value of \[\int_{0}^{\infty }{\frac{dx}{({{a}^{2}}+{{x}^{2}})}}\]is equal to:

    A)  \[\frac{\pi }{2}\]

    B)  \[\frac{\pi }{2a}\]

    C)  \[\frac{\pi }{a}\]

    D)  \[\frac{1}{2a}\]

    Correct Answer: B

    Solution :

    \[=\int_{0}^{\infty }{\frac{dx}{({{a}^{2}}+{{x}^{2}})}}=\left[ \frac{1}{a}{{\tan }^{-1}}\frac{x}{a} \right]_{0}^{\infty }\] \[=\frac{1}{a}\{{{\tan }^{-1}}(\infty )-{{\tan }^{-1}}(0)\}\] \[=\frac{1}{a}\left( \frac{\pi }{2}-0 \right)=\frac{\pi }{2a}\]


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