theorem Th11:
  |. (n|->r) - (n|->s) .| = sqrt(n) * |.r-s.|
  proof
    thus |. (n|->r) - (n|->s) .| = sqrt Sum sqr (n|->(r-s)) by RVSUM_1:30
    .= sqrt Sum (n|->(r-s)^2) by RVSUM_1:56
    .= sqrt (n*(r-s)^2) by RVSUM_1:80
    .= sqrt n * sqrt((r-s)^2) by SQUARE_1:29
    .= sqrt n * |.r-s.| by COMPLEX1:72;
  end;
