∀ {E : Type u_2} [inst : NormedAddCommGroup E] [inst_1 : NormedSpace ℂ E] {f : E → ℂ} {s : Set E} {x : E},
  DifferentiableWithinAt ℂ f s x → f x ∈ Complex.slitPlane → DifferentiableWithinAt ℂ (fun t => Complex.log (f t)) s x