
theorem Th07:
  for a being Real st 1 < a holds 1 / a - 1 < 0
  proof
    let a be Real;
    assume 1 < a;
    then 1 / a < 1 / 1 by XREAL_1:76;
    then 1 / a - 1 < 1 - 1 by XREAL_1:9;
    hence thesis;
  end;
