∀ {𝕜 : Type u_1} [inst : RCLike 𝕜] {n : Type u_2} [inst_1 : Fintype n] {A : Matrix n n 𝕜} [inst_2 : DecidableEq n]
  (hA : A.IsHermitian),
  A =
    ((Unitary.conjStarAlgAut 𝕜 (Matrix n n 𝕜)) hA.eigenvectorUnitary) (Matrix.diagonal (RCLike.ofReal ∘ hA.eigenvalues))