exact λ z hz => sub_ne_zero.mpr (ne_of_mem_sphere hz hr.ne.symm)
case hf
f g : ℂ → ℂ
p : FormalMultilinearSeries ℂ ℂ ℂ
z z₀ c : ℂ
n : ℕ
U : Set ℂ
r : ℝ
hU : IsOpen U
hr : 0 < r
h0 : closedBall z₀ r ⊆ U
h1 : DifferentiableOn ℂ g U
h2 : ∀ z ∈ closedBall z₀ r, g z ≠ 0
h3 : ∀ {z : ℂ}, z ∈ sphere z₀ r → deriv f z / f z = c / (z - z₀) + deriv g z / g z
e2 : sphere z₀ r ⊆ U
e4 : (∮ (z : ℂ) in C(z₀, r), deriv f z / f z) = ∮ (z : ℂ) in C(z₀, r), c / (z - z₀) + deriv g z / g z
⊢ ∀ x ∈ sphere z₀ r, id x - z₀ ≠ 0
no goals