根据点到已知坐标的两点的距离 获取该点坐标

    public class TowerCraneLocate
    {
        public static Point[] GetCoordinate(int L1, int L2)
        {
            if (L1 < L2)
            {
                return null;
            }
            else if (L1 == L2)
            {
                Point[] points = new Point[2];

                points[0].X = L2;
                points[0].Y = 0;
                points[1].X = -L2;
                points[1].Y = 0;

                return points;
            }
            else if (L2 == 0)
            {
                Point[] points = new Point[2];

                points[0].X = 0;
                points[0].Y = L1;
                points[1].X = 0;
                points[1].Y = -L1;

                return points;
            }
            else
            {
                Point[] points = new Point[4];

                int L3 = (int)Math.Round(Math.Sqrt(L1 * L1 - L2 * L2), 0);
                points[0].X = L2;
                points[0].Y = L3;
                points[1].X = -L2;
                points[1].Y = L3;
                points[2].X = L2;
                points[2].Y = -L3;
                points[3].X = -L2;
                points[3].Y = -L3;

                return points;
            }
        }

        public static Point[] GetCoordinate(Point pointA, int lA, Point pointB, int lB)
        {
            int dX = pointA.X - pointB.X;
            int dY = pointA.Y - pointB.Y;
            int lAB = (int)Math.Round(Math.Sqrt(dX * dX + dY * dY), 0);

            //如果两点重合
            if ((pointA.X == pointB.X) && (pointA.Y == pointB.Y))
            {
                return null;
            }

            //如果距离错误
            if ((lA + lB) < lAB)
            {
                return null;
            }

            //如果点在直线上
            if ((lA + lB) == lAB || Math.Abs(lA - lB) == lAB)
            {
                Point[] points = new Point[1];
                int ex = lA * dX / lAB;
                int ey = lA * dY / lAB;

                if ((lB - lA) == lAB)
                {
                    points[0].X = pointA.X + ex;
                    points[0].Y = pointA.Y + ey;
                }
                else
                {
                    points[0].X = pointA.X - ex;
                    points[0].Y = pointA.Y - ey;
                }
                return points;
            }
            else
            {
                pointB.X -= pointA.X;
                pointB.Y -= pointA.Y;

                double cita1;
                if (pointB.X == 0)
                {
                    if (pointB.Y > 0)
                        cita1 = 90;
                    else
                        cita1 = 270;
                }
                else if (pointB.Y == 0)
                {
                    if (pointB.X > 0)
                        cita1 = 0;
                    else
                        cita1 = 180;
                }
                else
                {
                    cita1 = Math.Atan(dY / (dX + 0.00001)) * 180 / Math.PI;
                    if (pointB.X < 0)
                        cita1 += 180;
                }

                double cita2 = Math.Acos((lAB * lAB + lA * lA - lB * lB) / (2 * lAB * lA * 0.99999)) * 180 / Math.PI;

                double x1 = Math.Cos((cita1 + cita2) * Math.PI / 180) * lA;
                double y1 = Math.Sin((cita1 + cita2) * Math.PI / 180) * lA;
                double x2 = Math.Cos((cita1 - cita2) * Math.PI / 180) * lA;
                double y2 = Math.Sin((cita1 - cita2) * Math.PI / 180) * lA;
                
                Point[] points = new Point[2];
                points[0].X = (int)Math.Round(x1,0) + pointA.X;
                points[0].Y = (int)Math.Round(y1,0) + pointA.Y;
                points[1].X = (int)Math.Round(x2,0) + pointA.X;
                points[1].Y = (int)Math.Round(y2,0) + pointA.Y;
                return points;
            }
        }
    }