simp
E : Type u_1
inst✝ : TopologicalSpace E
f : ℝ → ℝ
x : ℝ
hf : DifferentiableAt ℝ f x
⊢ cexp (f x • I) * (f x • deriv (fun x => I) x + deriv f x • I) = ↑(deriv f x) * I * cexp (f x • I)
E : Type u_1
inst✝ : TopologicalSpace E
f : ℝ → ℝ
x : ℝ
hf : DifferentiableAt ℝ f x
⊢ cexp (↑(f x) * I) * (↑(deriv f x) * I) = ↑(deriv f x) * I * cexp (↑(f x) * I)