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 Th35:
  A // C implies A is being_line & C is being_line
proof
  assume A // C;
  then ex a,b st A=Line(a,b) & a<>b & a,b // C;
  hence thesis;
end;
