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

theorem Th48:
  2RP.0 = 0 & 2RP.1 = 1
proof
  reconsider x = 0, y = 1 as Point of I[01] by BORSUK_1:43;
  thus 2RP.0 = 2RP.x .= 0 by Def6;
  thus 2RP.1 = 2 * y - 1 by Def6
    .= 1;
end;
