proposition: Lemma tau_is_uniform : forall (intruder evader : State) (t1 t2 : R), div_tau intruder evader <> 0%R -> tau intruder evader (t1 + t2) = (tau intruder evader t1 - t2)%R.
proof: Proof. intros; case (Req_EM_var (div_tau intruder evader) 0); intro; [ elim H; exact e | repeat rewrite tau_tmin; [ ring | exact H | exact H ] ]. Qed.
imports: Reals ails_def trajectory_const