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Homework Help: Commutator Relation

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  1. Jun 4, 2015 #1
    1. The problem statement, all variables and given/known data

    To show [J2, J+] = 0

    2. Relevant equations


    J+ = Jx + i Jy

    [J2, Jx ] = 0

    [J2, Jy ] = 0


    3. The attempt at a solution

    Step 1: L.H.S. = [J2, J+]

    Step 2: L.H.S. = [J2, Jx + i Jy ]

    Step 3: L.H.S. = [J2, Jx ] + i [J2, Jy ]

    Step 4: L.H.S. = 0 + 0

    Step 5: L.H.S. = 0

    L.H.S. = R.H.S.

    I'm kinda confuse about 'Step 3'. Can we take out the 'i' from whole bracket? If yes, then do I have to give any reason for it?
     
  2. jcsd
  3. Jun 4, 2015 #2
    Go ahead and write out the full commutator in step 2. What do you get?
     
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