proposition: Lemma class_rcoset x A y : x ^: (A :* y) = (x ^: A) :^ y.
proof: Proof. by rewrite -class_support_set1r classM. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)