reserve AS for AffinSpace;
reserve a,a9,b,b9,c,d,o,p,q,r,s,x,y,z,t,u,w for Element of AS;
reserve A,C,D,K for Subset of AS;

theorem Th33:
  a,b // A implies b,a // A
proof
  assume
A1: a,b // A;
  a<>b implies thesis by A1,Th1,Th31;
 hence thesis by A1;
end;
