simpa only [deriv_const'] using (hw.eventuallyEq_of_mem (hU.mem_nhds hz₀)).deriv_eq
case intro.intro
ι : Type u_1
l : Filter ι
U : Set ℂ
z₀✝ : ℂ
inst✝ : good_domain U
z₀ : ℂ
hz₀ : z₀ ∈ U
hU : IsOpen U
hU' : IsPreconnected U
h1 : ContinuousOn (obs z₀) (𝓙 U)
f : 𝓒 U
hf : f ∈ 𝓙 U
g : 𝓒 U
hg : g ∈ 𝓘 U
hfg : obs z₀ g ≤ obs z₀ f
w : ℂ
hw : EqOn f (fun x => w) U
⊢ deriv f z₀ = 0
no goals