proposition: Lemma cprod0g A : set0 \* A = set0.
proof: Proof. by rewrite /cprod centsC sub0set /pprod group0 trivg0 !if_same. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(choice fintype bigop finset fingroup morphism) mathcomp(quotient action)