question: public static double interiorAngle ( Coordinate p0 , Coordinate p1 , Coordinate p2 ) { double anglePrev = Angle . angle ( p1 , p0 ) ; double angleNext = Angle . angle ( p1 , p2 ) ; return Math . abs ( angleNext - anglePrev ) ; }
target:  Computes the interior angle between two segments of a ring. The ring is assumed to be oriented in a clockwise direction. The computed angle will be in the range [0, 2Pi]