proposition: Lemma repr_rcosetP x : rcoset_repr_spec x (repr (G :* x)).
proof: Proof. by rewrite -[repr _](mulgKV x); split; rewrite -mem_rcoset mem_repr_rcoset. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)