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Definition Ax2_R (intruder : State) : R :=
  (Rsqr (sind (heading intruder) * intruderSpeed) +
   Rsqr (- evaderSpeed + cosd (heading intruder) * intruderSpeed))%R.

Lemma Ax2_R_pos : forall intruder : State, (0 <= Ax2_R intruder)%R.