let E be non empty set ; :: thesis: for A, B being Subset of E holds A /\ B misses A /\ (B ` )
let A, B be Subset of E; :: thesis: A /\ B misses A /\ (B ` )
A /\ B misses A \ B by XBOOLE_1:89;
hence A /\ B misses A /\ (B ` ) by SUBSET_1:32; :: thesis: verum