theorem
  Ball(x,r) c= cl_Ball(x,r)
proof
  reconsider e = x as Point of Euclid n by TOPREAL3:8;
  Ball(x,r) = Ball(e,r) & cl_Ball(x,r) = cl_Ball(e,r) by Th11,Th12;
  hence thesis by METRIC_1:14;
end;
