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Homework Help: Commutation proof

  1. Apr 18, 2006 #1
    Hi there, I need a help on one of the commutation proof,
    the question is, show that [Lx,L^2]=0 cyclic where L=l1+l2
    The expression simplifies to [Lx,l1l2]+[Lx,l2l1] but I'm not sure if they are 0.
    Thanks for your help :D
  2. jcsd
  3. Apr 18, 2006 #2


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    What does L=l1+l2 mean ...?

  4. Apr 18, 2006 #3

    Meir Achuz

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    write L_x=L1_x+L2_x
    and expand L^2=(L1+L2)^2=...
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