theorem
  n <> 0 implies OpenHypercube(e,r) c= Ball(e,r*sqrt(n))
  proof
    assume
A1: n <> 0;
    then
A2: OpenHypercube(e,r*sqrt(n)/sqrt(n)) c= Ball(e,r*sqrt(n)) by Th17;
    r/sqrt(n)*sqrt(n) = r by A1,XCMPLX_1:87;
    hence thesis by A2,XCMPLX_1:74;
  end;
