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(* 02110-1301 USA                                                     *)
Unset Standard Proposition Elimination Names.
(**********)
Definition dx (intruder evader : State) (t : R) : R :=
(xt intruder + t * intruderSpeed * cosd (heading intruder) -
(xt evader + t * evaderSpeed))%R.
Definition dy (intruder evader : State) (t : R) : R :=
(yt intruder + t * intruderSpeed * sind (heading intruder) - yt evader)%R.
Definition dxdt (intruder : State) : R :=
(intruderSpeed * cosd (heading intruder) - evaderSpeed)%R.
Definition dydt (intruder : State) : R :=
(intruderSpeed * sind (heading intruder))%R.
Definition RR (intruder evader : State) (t : R) : R :=
sqrt (Rsqr (dx intruder evader t) + Rsqr (dy intruder evader t)).
Definition div_tau (intruder evader : State) : R :=
(Rsqr (dxdt intruder) + Rsqr (dydt intruder))%R.

(**********)
Lemma Req_EM_var : forall r1 r2 : R, {r1 = r2} + {r1 <> r2}.