proposition: Lemma rAU_ind_weak u s t : mprv (t ---> u) -> mprv (AX u ---> u) -> mprv ((AU s t) ---> u).
proof: Proof. move => A B. apply rAU_ind => //. rewrite -> B. by drop. Qed.
imports: mathcomp(all_ssreflect) CompDecModal.libs(edone base fset induced_sym) Setoid Morphisms Relation_Definitions