reserve x,y for set;
reserve X for non empty set;
reserve a,b,c,d for Element of X;
reserve S for OAffinSpace;
reserve a,b,c,d,p,q,r,x,y,z,t,u,w for Element of S;

theorem Th1:
  x,y // x,y
proof
  x,y // y,y by ANALOAF:def 5;
  hence thesis by ANALOAF:def 5;
end;
