theorem Th5: :: MULTOP_1:5

for A, B, C, D, E being non empty set
for f1, f2 being Function of [:A,B,C,D:],E st ( for a being Element of A
for b being Element of B
for c being Element of C
for d being Element of D holds f1 . [a,b,c,d] = f2 . [a,b,c,d] ) holds
f1 = f2