theorem Th44: :: MEASUR11:49

for X1, X2 being non empty set
for S1 being SigmaField of X1
for S2 being SigmaField of X2
for E being Element of sigma (measurable_rectangles (S1,S2)) holds
( ( for p being set holds X-section (E,p) in S2 ) & ( for p being set holds Y-section (E,p) in S1 ) )