theorem Th10: :: GOBRD11:10

for s1 being Real
for P1, P2 being Subset of (TOP-REAL 2) st P1 = { |[s,r]| where s, r is Real : s >= s1 } & P2 = { |[s2,r2]| where s2, r2 is Real : s2 < s1 } holds
P1 = P2 `