∀ {m : Type u_1} {𝔸 : Type u_4} [inst : Fintype m] [inst_1 : DecidableEq m] [inst_2 : NormedRing 𝔸] [NormedAlgebra ℚ 𝔸]
  [CompleteSpace 𝔸] (A B : Matrix m m 𝔸), Commute A B → NormedSpace.exp (A + B) = NormedSpace.exp A * NormedSpace.exp B