theorem Th62:
 for V being RealLinearSpace, p1,p2 being Point of V
  holds halfline(p1,p2) c= Line(p1,p2)
proof
 let V be RealLinearSpace, p1,p2 be Point of V;
 let e be object;
 assume e in halfline(p1,p2);
  then ex r st e =(1-r)*p1 + r*p2 & 0 <= r;
 hence e in Line(p1,p2);
end;
