Definition is_symmetric_pred :
  forall (F : field) (n : Nat), Predicate (Mmn F n n).Definition is_symmetric'_pred :
  forall (F : field) (n : Nat), Predicate (Mmn F n n).

Lemma symm_matr_subspace : forall (n : Nat) (F : field), is_subspace (is_symmetric_pred F n).