theorem Th38: :: STACKS_1:38

for X being StackAlgebra
for s being stack of X
for e being Element of X
for S being stack of (X /==)
for E being Element of (X /==) st S = Class ((==_ X),s) & E = e holds
( push (e,s) in push (E,S) & Class ((==_ X),(push (e,s))) = push (E,S) )