unfold MinT in |- *; unfold MaxT, tstep in |- *;
apply Rmult_lt_reg_l with 2%R...
prove_sup...
rewrite Rmult_0_r; rewrite Rmult_minus_distr_l; rewrite <- Rinv_r_sym...
apply Rlt_trans with 1%R; prove_sup...
Qed.

(**********)
Theorem rho_ub_t_PI2 :
forall (h : TypeSpeed) (t : TimeT), (rho_ub h * t < PI / 2)%R.