theorem Th19: :: AOFA_000:19

for A being Universal_Algebra
for B being Subset of A
for n being Nat holds B |^ (n + 1) = (B |^ n) \/ { ((Den (o,A)) . p) where o is Element of dom the charact of A, p is Element of the carrier of A * : ( p in dom (Den (o,A)) & rng p c= B |^ n ) }