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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Animesh anand
if you carefully see the 1st method then it is like a proof of method 2 . But there is no condition and it is not like any formula or any result which you needed to learn.It is totally depend on the given wave function that the what the expectation value comes.so you dont rely on 2nd method and need to go always with 1st method