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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Bidyut sinha
I have given detail calculation in the attached picture.
how 2 pi i is coming?
-2π.... Because first simplify it to the exponential form... which is exp(2iz)/z3...now expand it... after that obtain residue of this...and then evaluate the integral in such a way that contour will be around zero..then compare with imaginary part..you will get -2π