Convert azimuth to bearing

[AAverin]

Plotting this as lines on Mapbox, I need to calculate a second LatLng coordinate for the line.
One of the options is to do calculations using distance and bearing: https://stackoverflow.com/questions/7222382/get-lat-long-given-current-point-distance-and-bearing

Here is what I have tried (in Dart)

extension on num {
  num toDegrees() {
    return (this * 180 / PI);
  }
}

final toBearing = (num azimuthRad) {
//rotating 90 degrees, because azimuth, in the docs is 0 at south
//also making sure values are positive
    final azimuth = (azimuthRad.toDegrees() - 90) % 360;
//converting depending on the quadrant
    if (azimuth > 0 && azimuth <= 90) return azimuth;
    if (azimuth > 90 && azimuth <= 180) return 180 - azimuth;
    if (azimuth > 180 && azimuth <= 270) return azimuth - 180;
    if (azimuth > 270 && azimuth <= 360) return 360 - azimuth;
  };

Plotted values at the moment are way off and I am not sure where I went wrong. Any ideas?

[conradstephens]

Did you ever get anywhere with this? I'm currently trying to figure this out also

[AAverin]

No, not really