reserve T for non empty TopSpace,
  a, b, c, d for Point of T;

theorem Th61:
  for x being Point of I[01] holds [0,x] in IAA
proof
  let x be Point of I[01];
  0 is Point of I[01] & x <= 1 - 2 * 0 by BORSUK_1:43;
  hence thesis by Def8;
end;
