给定三个point abc c为ab的交点 求ab之间的角度

Question

public int test(point a,point b,point c)
{
   //......
}方法如何实现,我感觉我对不起我小学体育老师.C#角度两条直线point

Answer 1

求出ac的斜率，k1 = (a.y - c.y) / (a.x - c.x)
ac相对x轴的角度是a1 = arc tan k1
同理，k2 = (b.y - c.y) / (b.x - c.x)
a2 = arc tan k2
角度acb = a1 + a2

Answer 2

LZ知道余弦定理不？？ABC三点知道了，三边的长度也就知道了如图
公式

Answer 3

static float AngleInDegree(System.Drawing.Point p1, System.Drawing.Point p2, System.Drawing.Point p3)
        {
            System.Drawing.Point p12 = Normalize(Subtract(p1, p2));
            System.Drawing.Point p32 = Normalize(Subtract(p3, p2));
            return (float)(Math.Acos(Dot(p12, p32)) * 180 / Math.PI);
        }        static float Dot(System.Drawing.Point p1, System.Drawing.Point p2)
        {
            return p1.X * p2.X + p1.Y * p2.Y;
        }        static System.Drawing.Point Subtract(System.Drawing.Point p1, System.Drawing.Point p2)
        {
            return new System.Drawing.Point(p1.X - p2.X, p1.Y - p2.Y);
        }        static System.Drawing.Point Normalize(System.Drawing.Point p)
        {
            int length = (int)Math.Sqrt(p.X * p.X + p.Y * p.Y);
            if (length < 10e-6) throw new ArgumentException();
            return new System.Drawing.Point(p.X / length, p.Y / length);
        } class Program
    {
        static void Main(string[] args)
        {
            //调用类库：
            Point a = new Point { x = 0, y = 0};
            Point b = new Point { x = 10, y = 0};
            Point c = new Point { x = 0, y = 10};//2*Math.Sqrt(3) };
            double[] result = Angle.getAllAngle(a, b, c);
            Console.WriteLine(string.Format("a:{0}度, b:{1}度, c:{2}度", result[0], result[1], result[2]));
            Console.Read();
        }
    }
    //类库：
    public struct Point
    {
        public double x;
        public double y;
    }
    public static class Angle
    {
        public static double[] getAllAngle(Point a, Point b, Point c)
        {
            double[] result = new double[3];
            result[0] = getIntersectionAngle(b, c, a);
            result[1] = getIntersectionAngle(a, c, b);
            result[2] = getIntersectionAngle(a, b, c);
            return result;
        }
 
        public static double getIntersectionAngle(Point a, Point b, Point Intersection)
        {
            Point tempPoint1 = new Point { x = Intersection.x - a.x, y = Intersection.y - a.y};
            Point tempPoint2 = new Point { x = Intersection.x - b.x, y = Intersection.y - b.y};
 
            double temp = tempPoint1.x * tempPoint2.x + tempPoint1.y * tempPoint2.y;
            double temp2 = Math.Sqrt(Math.Pow(tempPoint1.x, 2) + Math.Pow(tempPoint1.y, 2));
            double temp3 = Math.Sqrt(Math.Pow(tempPoint2.x, 2) + Math.Pow(tempPoint2.y, 2));
            double tempCos = temp / (temp2 * temp3);
            double result = Math.Acos(tempCos);
 
            return Math.Round(((180 * result) / Math.PI),1);
        }
    }