intros; cut (i t <= vi intr * t)%R;
[ intros; unfold Rminus in |- *; rewrite Rplus_comm;
apply Rplus_le_reg_l with (vi intr * t)%R; repeat rewrite <- Rplus_assoc;
rewrite Rplus_opp_r; rewrite Rplus_0_l; rewrite Rplus_comm;
apply Rle_trans with (e t + i t)%R;
[ apply L_intruder | apply Rplus_le_compat_l; assumption ]
| unfold i in |- *; unfold Rsqr_intruder_distance in |- *;
apply (YCNGFTYS intr t H) ].
Qed.

Lemma YCNGSTYS_evader :
forall t : R,
(0 <= t)%R ->
(rho_vi * t < 2)%R -> (2 * r_vi * sin (rho_vi * (t / 2)) - l <= e t)%R.