proposition: Lemma eq_integral D g f : {in D, f =1 g} -> \int_(x in D) f x = \int_(x in D) g x.
proof: Proof. by rewrite /integral => /eq_restrictP->. Qed.
imports: HB(structures) mathcomp(all_ssreflect ssralg ssrnum ssrint interval finmap) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(cardinality fsbigop ) signed reals ereal topology normedtype sequences real_interval esum measure lebesgue_measure numfun