proposition: Lemma ab_diff : b [-] a [#] Zero.
proof: Proof. apply minus_ap_zero. apply Greater_imp_ap. exact Hab. Qed.
imports: ssreflect CSetoids CSetoidFun CFields CPolynomials Program Omega Equivalence Morphisms Wf Morphisms CRings CRing_Homomorphisms Rational Setoid CPoly_NthCoeff CPoly_Degree CReals Intervals CauchySeq IntervalFunct MoreIntervals MoreFunctions Composition seq bigopsClass Structures