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Finding an annihilator operator

  1. Oct 30, 2008 #1
    1. The problem statement, all variables and given/known data
    Find an annihilator operator for (cosx)^2

    2. Relevant equations

    3. The attempt at a solution
    first derivative -2cosxsinx
    second derivative 2(sinx)^2 - 2(cosx)^2
    third derivative 4sinxcosx +4cosxsinx

    This isn't getting me anywhere (D^2 + 2) is close but I still have the 2(sinx)^2 term.

    Any suggestions?
  2. jcsd
  3. Oct 30, 2008 #2


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    Science Advisor
    Homework Helper

    What's wrong with (D^3+4*D)? It's staring you in the face.
  4. Oct 30, 2008 #3
    Of course! I see it now. Thanks.
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