Probability and complex function: Unit IV: Complex integration

Singularities - residues residue theorem

Complex integration

If a function f (z) is analytic in a region R, is zero at a point z = z0 in R, then z0 is called a zero of f (z).

SINGULARITIES - RESIDUES RESIDUE THEOREM

 

1. Singularities - Classification

(a) Zeros of an Analytic function :

If a function f (z) is analytic in a region R, is zero at a point z = z0 in R, then z0 is called a zero of f (z).

(b) Simple zero

If f (z0) 0 and f' (z0) 0, then z = zo is called a simple zero of f(z) or a zero of the first order.

(c) Zero of order n

If f (z0) = f' (z0) = … fn-1 (z0) = 0 and fn (z0) ≠ 0, then z0 is called a zero of order n.

(or)

An analytic function f (z) is said to have a zero of order n, if f (z) can be expressed as f (z) = (z - z0)n p (z) where p (z) is analytic and (z0) ≠ 0.

 

Probability and complex function: Unit IV: Complex integration : Tag: : Complex integration - Singularities - residues residue theorem