proposition: Lemma fubini2 : \int[m2]_x G x = \int[m1 \x m2]_z f z.
proof: Proof. rewrite GE integralB; [|by[]|exact: integrable_Gplus|exact: integrable_Gminus]. by rewrite [in RHS]integralE ?fubini_tonelli2//; [exact: measurable_funeneg|exact: measurable_funepos]. 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