simpa [← mul_assoc] using this
E : Type u_1
inst✝ : TopologicalSpace E
f : ℝ → ℝ
f' x : ℝ
hf : HasDerivAt f f' x
this : HasDerivAt (fun x => cexp (f x • I)) (f' • (I * cexp (f x • I))) x
⊢ HasDerivAt (fun x => cexp (f x • I)) (↑f' * I * cexp (f x • I)) x
no goals