proposition: Lemma eq_integrable f g : {in D, f =1 g} -> mu_int f -> mu_int g.
proof: Proof. move=> fg /integrableP[mf fi]; apply/integrableP; split. exact: eq_measurable_fun mf. rewrite (le_lt_trans _ fi)//; apply: ge0_le_integral=> //. by apply: measurableT_comp => //; exact: eq_measurable_fun mf. by apply: measurableT_comp => //; exact: eq_measurable_fun mf. by move=> x Dx; rewrite fg// inE. 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