proposition: Lemma variationN a b f s : variation a b (\- f) s = variation a b f s.
proof: Proof. by rewrite /variation; apply: eq_bigr => k _ /=; rewrite -opprD normrN. Qed.
imports: mathcomp(all_ssreflect ssralg ssrint ssrnum finmap) mathcomp(matrix interval zmodp vector fieldext falgebra) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(cardinality) ereal reals signed topology prodnormedzmodule normedtype derive sequences real_interval HB(structures)