Proving Constant Time of "If and, then"

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Homework Statement



. Show that if
upload_2015-12-16_16-58-2.png
and
upload_2015-12-16_16-58-2.png
, then
upload_2015-12-16_16-58-2.png
is constant in time.

Homework Equations

The Attempt at a Solution

 
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d<A>/dt=i/h x ([H,A]) + dA/dt
Therefore if
upload_2015-12-16_17-12-9-png.93406.png
and dA/dt=0 , then dA/dt=0. Is this it.? :-(
 

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