theorem Th60: :: FUNCT_4:60

for X, X9, Y, Y9, Z, Z9 being set
for f being Function of [:X,Y:],Z
for g being Function of [:X9,Y9:],Z9 st Z <> {} & Z9 <> {} holds
|:f,g:| is Function of [:[:X,X9:],[:Y,Y9:]:],[:Z,Z9:]