
theorem THTU2:
  tau < 2
  proof
    |. tau_bar .| = - tau_bar by ABSVALUE:def 1; then
    (- tau_bar) -1 < 0 by XREAL_1:49,FIB_NUM4:5; then
    tau -2 +2 < 0+2 by XREAL_1:6;
    hence thesis;
  end;
