(1) The phrase "A is the union of B" is meaningless. "union" requires 2 or more arguments. If you mean "(A UNION B)" -- similar to your "(A INTERSECTION B)" -- then say so.
(2) Don't make us guess if "\" is supposed to mean the same thing as "/". The standard character for representing division is "/".
If you are serious about wanting help with your question, re-post it so we know for sure what the question is.