theorem Th48: :: MESFUN12:48

for X1, X2 being non empty set
for E being Subset of [:X1,X2:]
for x being Element of X1
for y being Element of X2 holds
( ProjPMap1 ((chi (E,[:X1,X2:])),x) = chi ((X-section (E,x)),X2) & ProjPMap2 ((chi (E,[:X1,X2:])),y) = chi ((Y-section (E,y)),X1) )