计算两点之间的角度的代码

/// 离心率 　　/// 返回两点间的角度
　　private double PointToAngle(Point AOrigin, Point APoint, double AEccentricity)
　　{
　　if (APoint.X == AOrigin.X)
if (APoint.Y > AOrigin.Y)
　　return Math.PI * 0.5;
　　else return Math.PI * 1.5;
　　else if (APoint.Y == AOrigin.Y)
　　if (APoint.X > AOrigin.X)
　　return 0;
　　else return Math.PI;
　　else
　　{
　　double Result = Math.Atan((AOrigin.Y - APoint.Y) /
　　(AOrigin.X - APoint.X) * AEccentricity);
　　if ((APoint.X <</SPAN> AOrigin.X) && (APoint.Y > AOrigin.Y))
　　return Result + Math.PI;
　　else if ((APoint.X <</SPAN> AOrigin.X) && (APoint.Y <</SPAN> AOrigin.Y))
　　return Result + Math.PI;
　　else if ((APoint.X > AOrigin.X) && (APoint.Y <</SPAN> AOrigin.Y))
　　return Result + 2 * Math.PI;
　　else return Result;
　　}
 
　　}