Compute all possible values of . Assume is positively oriented and none of the points lie on the simple closed curve .
So deform into . Then we have .
This is equaled to: .
Is this correct?
Yes, with the tiny correction:
using Cauchy's integral formula and calculating the residues for the separate singularities of the integrand. The integral has this value assuming encircles both 0, 1 and 2. Assuming any closed curve in the complex plane is possible, we keep all different combinations of the terms in the final sum, giving the possible values of the integral to be .
eg. If C encloses none of the singularites of f(z) then the integral is equal to zero. So one possible value of the inetrgal is zero.
Clearly there are several other possible values, depending on which and how many of the singularities are enclosed.