YRMax:

% Compute the maximum value of yR
 Such that the trajectory does not intersect avoidance region. 

 The inputs should observe the following constraints which are enforced in the
 safe guidance aglorithm:

 aE >= minDist + margin 
 yA >= aE / 2

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   Usage:
   [yRMax,aMin] = YRMax( yA, aE, minDist );

   Example:
   [yRMax,aMin] = YRMax( 45, 90, 60 );
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   ------
   Inputs
   ------
   yA            (1)   Current value of yA [m]
									(yA: cross-track offset at along-track axis crossing)
   aE            (1)   Current value of aE [m]
									(aE: semi-major axis of 2x1 in-plane ellipse)
   minDist       (1)   Minimum desired separation distance (in along-track) [m]

   -------
   Outputs
   -------
   yRMax         (1)   Maximum allowable value of yR [m]
									(yR: cross-track offset at radial-track axis crossing)
   aMin				(1) 	Phase angle where minimum distance ocurs [rad]

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