theorem Th27: :: MESFUN13:7

for X1, X2 being non empty set
for f being PartFunc of [:X1,X2:],ExtREAL
for x being Element of X1
for y being Element of X2 holds
( ProjPMap1 (|.f.|,x) = |.(ProjPMap1 (f,x)).| & ProjPMap2 (|.f.|,y) = |.(ProjPMap2 (f,y)).| )