proposition: Lemma axDBD s t : mprv (EX s ---> AX t ---> EX (s :/\: t)).
proof: Proof. rewrite /EX. do 3 Intro. Apply* 2. do 2 Rev. rewrite <- axN. apply: rNorm. do 3 Intro. Apply* 1. ApplyH axAI. Qed.
imports: mathcomp(all_ssreflect) CompDecModal.libs(edone base fset induced_sym) Setoid Morphisms Relation_Definitions