check sweep (angle between velI and lift-drag-plane)

[Simon]

Why does this line use the asin function instead of acos?

  // check sweep (angle between velI and lift-drag-plane)
  double sinSweepAngle = ignition::math::clamp(
      spanwiseI.Dot(velI), minRatio, maxRatio);

  this->sweep = asin(sinSweepAngle);

PX4-SITL_gazebo-classic/src/liftdrag_plugin/liftdrag_plugin.cpp

Line 252 in f754540

 this->sweep = asin(sinSweepAngle); 

[Simon]

@pjdewitte @Jaeyoung-Lim

[Jaeyoung Lim]

@mengchaoheng Why should it use cos?

[Simon]

o, I get it. thanks !