∀ {𝕜 : Type u_1} [inst : RCLike 𝕜] {F : Type u_2} [inst_1 : SeminormedAddCommGroup F] [inst_2 : NormedSpace 𝕜 F]
  [inst_3 : NormedSpace ℝ F] [inst_4 : IsScalarTower ℝ 𝕜 F] (fr : StrongDual ℝ F) (x : F),
  (ContinuousLinearMap.extendTo𝕜' fr) x = ↑(fr x) - RCLike.I * ↑(fr (RCLike.I • x))