simp_rw [← Complex.real_smul]
E : Type u_1
inst✝ : TopologicalSpace E
f : E → ℝ
hf : Continuous f
⊢ Continuous fun x => cexp (↑(2 * π * f x) * I)
E : Type u_1
inst✝ : TopologicalSpace E
f : E → ℝ
hf : Continuous f
⊢ Continuous fun x => cexp ((2 * π * f x) • I)