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Check at problem 3.4 the relation that he gives between operator A and state φn.
Now check the relation that he uses in problem 3.5 between A and φn again.
They are different while on the announcement of prob 3.5 he does not mention any change of this relation.
The Attempt at a Solution
Is there any misprint or am i that dumb that cannot understand some change of the relation that he implies?