proposition: Lemma continuity_in_contravariant : forall D E f, included D E -> continuity_in E f -> continuity_in D f.
proof: Proof. intros D E f inc f_cont x ; apply continuity_pt_in_contravariant with E, f_cont ; assumption. Qed.
imports: Rbase Ranalysis Rinterval Rfunctions Rfunction_def Ranalysis_def Rfunction_facts MyRIneq MyR_dist Lra