proposition: Lemma invg_lcoset x : (x *: G)^-1 = G :* x^-1.
proof: Proof. by rewrite invMg invGid invg_set1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)