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Trig substitution ∫(4x^3)/√(x^2+4)

  1. Sep 10, 2012 #1
    1. The problem statement, all variables and given/known data


    2. Relevant equations

    3. The attempt at a solution

    So, I let x= 2tanθ
    dx= 2sec^2θ dθ
    So, √(4tan^2(θ)+4)=2secθ

    Would it go to ∫16tan^3(θ)2sec(θ)dθ
    or ∫32tan^3(θ)sec(θ)dθ
  2. jcsd
  3. Sep 10, 2012 #2


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    Gold Member

    It is correct so far.

  4. Sep 10, 2012 #3


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    Science Advisor
    Homework Helper

    I don't think you really need a trig substitution here. Try u=x^2+4 first.
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