C#求圆周上一点绕圆心旋转后坐标

    x'= (x - rx0)*cos(RotaryAngle) + (y - ry0)*sin(RotaryAngle) + rx0 ;
    y'=-(x - rx0)*sin(RotaryAngle) + (y - ry0)*cos(RotaryAngle) + ry0 ;

/// <summary>
/// 旋转后坐标
/// </summary>
/// <param name="center">圆心坐标</param>
/// <param name="fpoint">旋转前坐标</param>
/// <param name="alg">旋转角度</param>
/// <returns>旋转后坐标</returns>
mPoint PointRotate(mPoint center, mPoint fpoint, double alg)
{
mPoint lpoint;
alg = (alg / 180.0) * Math.PI;
double a = Math.Cos(alg);
double b = Math.Sin(alg);
lpoint.X = (fpoint.X - center.X) * a + (fpoint.Y - center.Y) * b + center.X;
lpoint.Y = -(fpoint.X - center.X) * b + (fpoint.Y - center.Y) * a + center.Y;
return lpoint;
}