let T be non empty TopSpace; :: thesis: for F being Subset-Family of T holds Int (Cl (Int (meet F))) c= meet (Int (Cl (Int F)))
let F be Subset-Family of T; :: thesis: Int (Cl (Int (meet F))) c= meet (Int (Cl (Int F)))
A1: Int (Cl (Int (meet F))) c= Int (meet (Cl (Int F))) by Th49, TOPS_1:19;
Int (meet (Cl (Int F))) c= meet (Int (Cl (Int F))) by Th28;
hence Int (Cl (Int (meet F))) c= meet (Int (Cl (Int F))) by A1; :: thesis: verum