∀ {E : Type u_1} [inst : NormedAddCommGroup E] [inst_1 : NormedSpace ℂ E] {f : ℂ → E} {x : ℂ} {s : Set ℂ},
  DifferentiableWithinAt ℝ f s x →
    ∀ (h₂ : (fderivWithin ℝ f s x) Complex.I = Complex.I • (fderivWithin ℝ f s x) 1),
      UniqueDiffWithinAt ℝ s x → fderivWithin ℂ f s x = (fderivWithin ℝ f s x).complexOfReal h₂