let X be non empty set ; for S being SigmaField of X
for M being sigma_Measure of S
for E being Element of S
for f being b3 -measurable PartFunc of X,ExtREAL st dom f c= E & f is_a.e.integrable_on M holds
f is_integrable_on M
let S be SigmaField of X; for M being sigma_Measure of S
for E being Element of S
for f being b2 -measurable PartFunc of X,ExtREAL st dom f c= E & f is_a.e.integrable_on M holds
f is_integrable_on M
let M be sigma_Measure of S; for E being Element of S
for f being b1 -measurable PartFunc of X,ExtREAL st dom f c= E & f is_a.e.integrable_on M holds
f is_integrable_on M
let E be Element of S; for f being E -measurable PartFunc of X,ExtREAL st dom f c= E & f is_a.e.integrable_on M holds
f is_integrable_on M
let f be E -measurable PartFunc of X,ExtREAL; ( dom f c= E & f is_a.e.integrable_on M implies f is_integrable_on M )
assume that
A1:
dom f c= E
and
A2:
f is_a.e.integrable_on M
; f is_integrable_on M
reconsider E1 = dom f as Element of S by A2, Th16;
consider A being Element of S such that
A3:
( M . A = 0 & A c= dom f & f | (A `) is_integrable_on M )
by A2;
A4:
f | (A `) = f | ((dom f) \ A)
by Th15;
then A5:
dom (f | (A `)) = (dom f) /\ ((dom f) \ A)
by RELAT_1:61;
then A6: dom (f | (A `)) =
(E1 /\ E1) \ A
by XBOOLE_1:49
.=
E1 \ A
;
then A7:
( dom (max+ (f | (A `))) = E1 \ A & dom (max- (f | (A `))) = E1 \ A )
by MESFUNC2:def 2, MESFUNC2:def 3;
A8:
f is E1 -measurable
by A1, MESFUNC1:30;
then
f is E1 \ A -measurable
by XBOOLE_1:36, MESFUNC1:30;
then
f | (A `) is E1 \ A -measurable
by A4, A5, A6, MESFUNC5:42;
then A9:
( max+ (f | (A `)) is E1 \ A -measurable & max- (f | (A `)) is E1 \ A -measurable )
by A6, MESFUNC2:25, MESFUNC2:26;
A10:
( E1 = dom (max+ f) & E1 = dom (max- f) )
by MESFUNC2:def 2, MESFUNC2:def 3;
A11:
( max+ f is nonnegative & max- f is nonnegative )
by MESFUN11:5;
( Integral (M,((max+ f) | ((dom f) \ A))) = Integral (M,(max+ f)) & Integral (M,((max- f) | ((dom f) \ A))) = Integral (M,(max- f)) )
by A3, A8, A10, MESFUNC2:25, MESFUNC2:26, MESFUNC5:95;
then
( Integral (M,(max+ (f | (A `)))) = Integral (M,(max+ f)) & Integral (M,(max- (f | (A `)))) = Integral (M,(max- f)) )
by A4, MESFUNC5:28;
then
( integral+ (M,(max+ (f | (A `)))) = Integral (M,(max+ f)) & integral+ (M,(max- (f | (A `)))) = Integral (M,(max- f)) )
by A7, A9, MESFUNC5:88, MESFUN11:5;
then A12:
( integral+ (M,(max+ (f | (A `)))) = integral+ (M,(max+ f)) & integral+ (M,(max- (f | (A `)))) = integral+ (M,(max- f)) )
by A8, A10, A11, MESFUNC2:25, MESFUNC2:26, MESFUNC5:88;
( integral+ (M,(max+ (f | (A `)))) < +infty & integral+ (M,(max- (f | (A `)))) < +infty )
by A3, MESFUNC5:def 17;
hence
f is_integrable_on M
by A8, A12, MESFUNC5:def 17; verum