1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    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!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook