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Help with an integral

  1. Oct 5, 2012 #1
    Hi!
    I'm studying Sterman-Weinberg Jets in QFT and I came about with this integral. Despite it is very simple, I can't solve it.
    The integral is
    [tex]
    \int_{\theta=\pi-\delta}^{\theta=\pi}\frac{d\cos (\theta)}{1-\cos^2(\theta)}
    [/tex]
    Solving it I get
    [tex]
    \frac{1}{2}\left[\log\left(\frac{1+\cos\delta}{1-\cos\delta}\right)-\log\left(\frac{1-\cos\delta}{1+\cos\delta}\right)\right]
    [/tex]
    However, the text states that the result is proportional to
    [tex]
    \log\delta^2
    [/tex]

    Any ideas?
     
  2. jcsd
  3. Oct 5, 2012 #2
    I get the correct result. [itex]\log\delta^2[/itex] follows from the approximation [itex]\delta<<1[/itex].
     
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