fact: Parameter add_DN_correct : forall p x y, valid_lb x = true -> valid_lb y = true -> (valid_lb (add_DN p x y) = true /\ le_lower (toX (add_DN p x y)) (Xadd (toX x) (toX y))).
imports: Coq(ZArith Reals) Flocq(Zaux Raux) Xreal Basic