Consider

On the second line I am wondering how the first two terms go to 0 and how the third term

etc?

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- February 23rd 2011, 01:13 PMbugatti79Quantum Mechanics - Angular Momentum part 2
Consider

On the second line I am wondering how the first two terms go to 0 and how the third term

etc? - February 23rd 2011, 01:27 PMAckbeet
Any operator commutes with itself, which is another way of saying its commutator is zero. As for your second question, note that

Also, note that, in general,

Hence, you have

Does that make sense?