C#求两条线段的角度

Question

GDI+，C#

Answer 1

atan2反正切，你看看这个函数的用法，就知道参数是干嘛的了

Answer 2

ya2 ya1都是点的坐标，这些都是数学知识，跟程序无关，翻译C#如下：
            Point a1 = new Point(0, 3);    //A线段端点a1
            Point a2 = new Point(4, 6);     //端点a2
            Point b1 = new Point(-1, 1);   // 线段端点b1
            Point b2 = new Point(-1, 2);    //线段端点b2
            var A = Math.Atan2(a2.Y - a1.Y, a2.X - a1.X);
            var B = Math.Atan2(b2.Y - b1.Y, b2.X - b1.X);
            var C = B - A;

Answer 3

向量A与向量B的点积 等于 向量A的长度乘以向量B的长度再乘以向量A与向量B的夹角的余弦值A·B= |A|*|B|* cos(angle)//弧度
angle=acos((A·B)/(|A|*|B|))//转成角度
angle=(180 * System.Math.Acos(angle)) / System.Math.PIvector2(x,y) 
线段a的向量: va=va2-va1  va2=(xa2,ya2)   va1=(xa1,ya1)
线段b的向量: vb=vb2-vb1  vb2=(xb2,yb2)   va1=(xb1,yb1)

Answer 4

 private void pictureBox1_MouseClick(object sender, MouseEventArgs e)
        {
            
            if (Dotter == 1)
            {
                dot1.Visible = true;
                dot1.Location = e.Location;
                Dotter = 2;
            }
            else if (Dotter == 2)
            {
                dot2.Visible = true;
                dot2.Location = e.Location; 
                Dotter = 3;
                Graphics g = this.pictureBox1.CreateGraphics();
                Pen p = new Pen(Color.Black, 2);
                g.DrawLine(p, dot1.Location, dot2.Location);
            }
            else if (Dotter == 3)
            {
                dot3.Visible = true;
                dot3.Location = e.Location;
                Dotter = 4;            }
            else if (Dotter == 4)
            {
                dot4.Visible = true;
                dot4.Location = e.Location;
                Dotter = 5;
                Graphics g = this.pictureBox1.CreateGraphics();
                Pen p = new Pen(Color.Black, 2);
                g.DrawLine(p, dot3.Location, dot4.Location);
                anglesize.Text = (Angle1(dot1.Location, dot2.Location, dot3.Location,dot4.Location)).ToString() + "°";
            }
            else if (Dotter==5)
            {
                dot1.Visible = false;
                dot2.Visible = false;
                dot3.Visible = false;
                dot4.Visible = false;
                Dotter = 1;
            }
        }
 private static float Angle1(Point first, Point second, Point third, Point fourth)
        {            var A = Math.Atan2(second.Y - first.Y, second.X - first.X);
            var B = Math.Atan2(fourth.Y - third.Y, fourth.X - third.X);
            return (float)(B - A);
            
        }
这样为什么得不出来角度，只能得到一个零点几的小数点。不知道哪里出了问题

Answer 5

return (float)(B - A);
==>>
return (180 * (float)(B - A)) / Math.PI

Answer 6

return (float)(B - A);
==>>
return (180 * (float)(B - A)) / Math.PI

、多谢！解决了！另外想问下，鼠标点在pictureBox上想出现一个点或者自定义小圈圈怎么做到啊？