proposition: Lemma trace_mx11 (A : 'M_1) : \tr A = A 0 0.
proof: Proof. by rewrite {1}[A]mx11_scalar mxtrace_scalar. 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)