
theorem THY1:
  dist(|[0,0]|,|[1,0]|) = 1
  proof
    dist(|[0,0]|,|[1,0]|) = sqrt ((0-1)^2+(0 - 0)^2) by THYQ
                         .= sqrt ((-1) * (-1) + 0^2) by SQUARE_1:def 1
                         .= sqrt (1 + 0 * 0) by SQUARE_1:def 1
                         .= 1;
    hence thesis;
  end;
