
theorem THY2:
  dist(|[0,0]|,|[0,1]|) = 1
  proof
    dist(|[0,0]|,|[0,1]|) = sqrt ((0-0)^2+(0 - 1)^2) by THYQ
                         .= sqrt (0 * 0 + (-1)^2) by SQUARE_1:def 1
                         .= sqrt (0 + (-1) * (-1)) by SQUARE_1:def 1
                         .= 1;
    hence thesis;
  end;
