
theorem Th87:
for G being SimpleGraph holds union G in union Mycielskian G
proof
 let G be SimpleGraph;
 union G in {union G} by TARSKI:def 1;
 then union G in (union G) \/ [:union G,{union G}:] \/ {union G}
    by XBOOLE_0:def 3;
 hence union G in union Mycielskian G by Th86;
end;
