- #1
hoch449
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Homework Statement
I am supposed to find if the following commutes: [Lx,Ly]
Homework Equations
Lx= -i[tex]\hbar[/tex][y([tex]\partial/[/tex][tex]\partial[/tex]z) - z([tex]\partial/[/tex][tex]\partial[/tex]y)]
Ly= -i[tex]\hbar[/tex][z([tex]\partial/[/tex][tex]\partial[/tex]x) - x([tex]\partial/[/tex][tex]\partial[/tex]z)]
where [Lx,Ly]=LxLy-LyLx
If it commutes then [Lx,Ly]=0
The Attempt at a Solution
[Lx,Ly]= (i[tex]\hbar[/tex])2{[y([tex]\partial/[/tex][tex]\partial[/tex]z) - z([tex]\partial/[/tex][tex]\partial[/tex]y)[z([tex]\partial/[/tex][tex]\partial[/tex]x) - x([tex]\partial/[/tex][tex]\partial[/tex]z)]}
After expanding this I got a result of 0. So my solution concluded that they commute.
The answer however is [Lx,Ly]= i[tex]\hbar[/tex]Lx
I clearly expanded it wrong. I was hoping if anyone could explain how they expanded the LxLy-LyLx part. In my calculations I cannot seem to figure out how the answer contains a few more parts in the expansion which results in a non-commutation..
Thanks!