reserve AS for AffinSpace;
reserve a,b,c,d,a9,b9,c9,d9,p,q,r,x,y for Element of AS;
reserve A,C,K,M,N,P,Q,X,Y,Z for Subset of AS;

theorem Th11:
  ex A st a in A & b in A & A is being_line
proof
  LIN a,b,b by AFF_1:7;
  then ex A st A is being_line & a in A & b in A & b in A by AFF_1:21;
  hence thesis;
end;
