proposition: Lemma fmM_eq1 m1 m2 : (m1 * m2 == 1)%M = (m1 == 1%M) && (m2 == 1%M).
proof: Proof. by rewrite -!fdeg_eq0 fdegM addn_eq0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap