proposition: Lemma is_perm_mx_tr n (A : 'M_n) : is_perm_mx A^T = is_perm_mx A.
proof: Proof. apply/is_perm_mxP/is_perm_mxP=> [[t def_t] | [t ->]]; exists t^-1%g. by rewrite -tr_perm_mx -def_t trmxK. by rewrite tr_perm_mx. 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)