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        /// <summary>
        /// 求角度
        /// </summary>
        /// <param name="cen"></param>
        /// <param name="first"></param>
        /// <param name="second"></param>
        /// <returns></returns>
        public static double GetAngleWith360(DPoint3 cen, DPoint3 first, DPoint3 second)
        {
            //计算角度
            double ma_x = first.x - cen.x;
            double ma_y = first.y - cen.y;
            double mb_x = second.x - cen.x;
            double mb_y = second.y - cen.y;
            double v1 = (ma_x * mb_x) + (ma_y * mb_y);
            double ma_val = Math.Sqrt(ma_x * ma_x + ma_y * ma_y);
            double mb_val = Math.Sqrt(mb_x * mb_x + mb_y * mb_y);
            double cosM = v1 / (ma_val * mb_val);
            if (cosM < -1)
            {
                cosM = -1;
            }
            else if (cosM > 1)
            {
                cosM = 1;
            }
            double angleAMB = Math.Acos(cosM) * 180 / Math.PI;

            //计算两条线向量的顺逆时针方向
            DPoint3 lineFirst = new DPoint3(first.x - cen.x, first.y - cen.y, 0);
            DPoint3 lineSecond = new DPoint3(second.x - cen.x, second.y - cen.y, 0);
            bool isClockwise = lineFirst.x * lineSecond.y - lineSecond.x * lineFirst.y < 0;
            if (isClockwise)
            {
                angleAMB = 360 - angleAMB;
            }
            return angleAMB;
        }