proposition: Lemma trmx_inj : forall m n (A B : 'M_(m, n)), trmx A === trmx B -> A === B.
proof: Proof. by rewrite/trmx=> m n A B eqtr i j; apply eqtr. Qed.
imports: ssreflect ssrbool ssrfun eqtype ssrnat seq choice fintype finfun bigops ssralg groups perm zmodp morphisms Ring RingClass bigopsClass Setoid Morphisms