let T be TopStruct ; :: thesis: for A, B being Subset of T holds Cl (A /\ B) c= (Cl A) /\ (Cl B)
let A, B be Subset of T; :: thesis: Cl (A /\ B) c= (Cl A) /\ (Cl B)
( Cl (A /\ B) c= Cl A & Cl (A /\ B) c= Cl B ) by Th19, XBOOLE_1:17;
hence Cl (A /\ B) c= (Cl A) /\ (Cl B) by XBOOLE_1:19; :: thesis: verum