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How do I carry out an approximation for this equation?(if L Ns then what?)

  1. May 6, 2012 #1

    What does that reduce to if L << Ns ? Obviously setting L to zero leads me nowhere since that argument above is actually inside a logarithm. I don't know how to perform the approximation. And the answer can't be zero by the way. Is there something I can do here? Usually the only approximations I've done before are just expansions but this is already expanded.

    Thank you.
  2. jcsd
  3. May 6, 2012 #2


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    Science Advisor
    Homework Helper

    You can write it as
    $$\frac{1 - L/N_s}{1 + L/N_s}$$
    and then use the Binomial theorem on ##(1 + L/N_s)^{-1}##.
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