TwoDOptimalSailAngle:

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   Generates the optimal sail angle for planar problems.

   Since version 7.
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   Form:
   alpha = TwoDOptimalSailAngle( x, t )
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   Inputs
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   x          (:,:)  [r;u;v;lambdaR;lambdaU;lambdaV];
   t          (1,:)  Time

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   Outputs
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   alpha      (1,:)  Sail in plane angle (rad)  

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