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Homework Help: Derivative of a complex conjugate?

  1. Sep 20, 2010 #1
    1. The problem statement, all variables and given/known data

    [PLAIN]http://img823.imageshack.us/img823/4500/85131172.png [Broken]

    2. Relevant equations

    Derivations and substitutions.

    3. The attempt at a solution

    Basically it seems like a very simple problem to me however I can't seem to get the right answer. First I just assumed that the c.c. (complex conjugate) was just a constant thus:

    [tex]\Psi[/tex]'(x) = Ckeikx
    [tex]\Psi[/tex]''(x) = Ck2eikx

    But substituting that equation into the original DE gives:

    Ck2eikx = Ck2eikx + k2(c.c)

    obviously I'm missing something.

    edit: maybe I read the question wrong could c.c. mean Ce-ikx ???
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Sep 20, 2010 #2


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    Science Advisor
    Homework Helper

    Yes, the complex conjugate of exp(ikx) is exp(-ikx). And don't forget the c.c. of C is C^*. And d/dx(exp(ikx)) isn't k*exp(ikx) either, it's ik*exp(ikx).
  4. Sep 20, 2010 #3
    Ok, I understand now. Also thanks for pointing out my derivative mistake!
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