theorem Th86: :: TDLAT_2:87

for T being non empty TopSpace
for a, b being Element of (Domains_Lattice T)
for A, B being Element of Domains_of T st a = A & b = B holds
( a "\/" b = (Int (Cl (A \/ B))) \/ (A \/ B) & a "/\" b = (Cl (Int (A /\ B))) /\ (A /\ B) )