fact: Hypothesis DDf_ge0 : forall x, a < x < b -> 0 <= DDf x.
imports: mathcomp(all_ssreflect ssralg ssrint ssrnum finmap) mathcomp(matrix interval zmodp vector fieldext falgebra) mathcomp(mathcomp_extra boolp classical_sets set_interval) mathcomp(functions cardinality) ereal reals signed topology prodnormedzmodule normedtype derive realfun itv HB(structures)