reserve a,b,r for non unit non zero Real;
reserve X for non empty set,
        x for Tuple of 4,X;
reserve V             for RealLinearSpace,
        A,B,C,P,Q,R,S for Element of V;

theorem Th05:
  P,Q,Q are_collinear
  proof
    P in Line(P,Q) & Q in Line(P,Q) by RLTOPSP1:72;
    hence thesis;
  end;
