English
For f continuous on a closed disk and differentiable off a countable interior, the circle integral of f(z)/(z − w) equals 2πi f(w).
Русский
Для f непрерывной на замкненном диске и дифференцируемой вне счётного множества внутри, круговой интеграл f(z)/(z − w) dz равен 2πi f(w).
LaTeX
$$$\\oint_{z\\in C(c,R)} \\dfrac{f(z)}{z-w} \\, dz = 2 \\pi i \\cdot f(w)$$$
Lean4
/-- A complex differentiable function `f : ℂ → E` is continuously differentiable at every point. -/
protected theorem _root_.Differentiable.contDiff {f : ℂ → E} (hf : Differentiable ℂ f) {n : WithTop ℕ∞} :
ContDiff ℂ n f :=
contDiff_iff_contDiffAt.mpr fun z ↦ (hf.analyticAt z).contDiffAt