void Calculate_cicular(Point px1, Point px2, Point px3,out Point center,out double r)
{
    int x1, y1, x2, y2, x3, y3;
    int a, b, c, g, e, f;
    x1 = px1.X;//定义点的坐标
    y1 = px1.Y;
    x2 = px2.X;
    y2 = px2.Y;
    x3 = px3.X;
    y3 = px3.Y;
    e = 2 * (x2 - x1);
    f = 2 * (y2 - y1);
    g = x2 * x2 - x1 * x1 + y2 * y2 - y1 * y1;
    a = 2 * (x3 - x2);
    b = 2 * (y3 - y2);
    c = x3 * x3 - x2 * x2 + y3 * y3 - y2 * y2;
     center = new Point();
    center.X = (g * b - c * f) / (e * b - a * f);
    center.Y = (a * g - c * e) / (a * f - b * e);
     r = Math.Sqrt((center.X - x1) * (center.X - x1) + (center.Y - y1) * (center.Y - y1));
}