proposition: Lemma dmA s t : mprv (~~: (s :/\: t) <--> (~~: s) :\/: (~~: t)).
proof: Proof. rewrite /Or /And. rule axAI; by do ! rewrite -> axDNE. Qed.
imports: mathcomp(all_ssreflect) CompDecModal.libs(edone base fset induced_sym) Setoid Morphisms Relation_Definitions