proposition: Lemma invg_rcoset x : (G :* x)^-1 = x^-1 *: G.
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)