proposition: Lemma is_diag_trmx m n (A : 'M[V]_(m, n)) : is_diag_mx A^T = is_diag_mx A.
proof: Proof. by rewrite !is_diag_mxEtrig trmxK andbC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg countalg finalg zmodp)