theorem Th15: :: JORDAN2B:15

for n being Element of NAT
for a, b being Real
for f being Function of (TOP-REAL n),R^1
for i being Element of NAT st ( for p being Element of (TOP-REAL n) holds f . p = p /. i ) holds
f " { s where s is Real : ( a < s & s < b ) } = { p where p is Element of (TOP-REAL n) : ( a < p /. i & p /. i < b ) }