theorem :: MESFUN6C:43

for X being non empty set
for S being SigmaField of X
for M being sigma_Measure of S
for f being PartFunc of X,COMPLEX st ex A being Element of S st
( A = dom f & f is A -measurable ) & f is_integrable_on M holds
|.(Integral (M,f)).| <= Integral (M,|.f.|)