Residue at infinity from an asymptotic constant Created 2026-09-24 Updated 2026-11-05
Suppose is holomorphic outside a disk and uniformly as . Thenwith counterclockwise large circles. The conventional residue at infinity has the opposite sign from the coefficient extracted by that counterclockwise circle.
To check the sign, use . The differential becomes , whose residue at zero is . Alternatively, , and the large-circle contour estimate makes the error integral vanish. For the constant function , the integral is but the residue at infinity is .