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 Th14:
  a in Line(a,b) & b in Line(a,b)
proof
A1: LIN a,b,b by Th6;
  LIN a,b,a by Th6;
  hence thesis by A1,Def2;
end;
