Residues and the residue theorem
The residue at an isolated singularity is the (z−a)⁻¹ coefficient of its Laurent series.
Key knowledge
The residue at an isolated singularity is the (z−a)⁻¹ coefficient of its Laurent series. For a positively oriented simple closed contour enclosing finitely many such singularities, ∮f(z)dz=2πi times the sum of their residues.
Conditions and scope
- f is holomorphic on a neighborhood of the closed interior except at those isolated points; none lies on the contour.
- Branch cuts and nonisolated singularities require another formulation.
Sources · 1
References
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Evidence and review
Topic 8 section 8.4 residue definition and section 8.5 residue theorem/proof, printed10–11.
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