proposition: Lemma mxtrace_tr A : \tr A^T = \tr A.
proof: Proof. by apply: eq_bigr=> i _; rewrite mxE. 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)