proposition: Lemma axEUeq s t : mprv (EU s t <--> t :\/: s :/\: EX (EU s t)).
proof: Proof. rewrite /EU /EX. rewrite -> axDNE, axAReq at 1. rewrite -> dmA,dmO at 1. by do ! rewrite -> axDNE. Qed.
imports: mathcomp(all_ssreflect) CompDecModal.libs(edone base fset induced_sym) Setoid Morphisms Relation_Definitions