theorem Th14:
  K is being_line implies P c= Plane(K,P)
proof
  assume
A1: K is being_line;
    let x be object;
    assume
A2: x in P;
    then reconsider a=x as Element of AS;
    a,a // K by A1,AFF_1:33;
    hence x in Plane(K,P) by A2;
end;
