reserve A,X,X1,X2,Y,Y1,Y2 for set, a,b,c,d,x,y,z for object;
reserve P,P1,P2,Q,R,S for Relation;

theorem
  for S being Relation, R being X-defined Relation st R c= S holds R c= S|X
proof let S be Relation, R be X-defined Relation;
  R = R|X;
  hence thesis by Th70;
end;
