fact: Definition sigma_sub_additive := forall (A : set T) (F : nat -> set T), (forall n, measurable (F n)) -> measurable A -> A `<=` \bigcup_n F n -> mu A <= \sum_(n <oo) mu (F n).
imports: mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(cardinality fsbigop ) reals ereal signed topology normedtype sequences esum numfun HB(structures)