theorem :: MESFUNC6:103
for X being non empty set
for S being SigmaField of X
for M being sigma_Measure of S
for f, g being PartFunc of X,REAL
for B being Element of S st f is_integrable_on M & g is_integrable_on M & B c= dom (f + g) holds
( f + g is_integrable_on M & Integral_on (M,B,(f + g)) = (Integral_on (M,B,f)) + (Integral_on (M,B,g)) )