theorem Th52: :: MESFUN15:50

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,ExtREAL
for A, B being set st A c= dom f & B c= dom f & f | A is_integrable_on M & f | B is_integrable_on M holds
f | (A \/ B) is_integrable_on M