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 Th2:
  x,y // z,t implies y,x // t,z & z,t // x,y & t,z // y,x
proof
  assume x,y // z,t;
  hence y,x // t,z & z,t // x,y by Lm1,ANALOAF:def 5;
  hence thesis by ANALOAF:def 5;
end;
