using System;

​

public class Program

{

    public static void Main()

    {   

        var angle = 180 * Math.PI/180;

        Console.WriteLine(rotate_point(0,0,angle,new Point{X=10, Y=10}).Print());

    }

​

    static Point rotate_point(double cx, double cy, double angle, Point p)

    {

        double s = Math.Sin(angle);

        double c = Math.Cos(angle);

        // translate point back to origin:

        p.X -= cx;

        p.Y -= cy;

        // rotate point

        double Xnew = p.X * c - p.Y * s;

        double Ynew = p.X * s + p.Y * c;

        // translate point back:

        p.X = Xnew + cx;

        p.Y = Ynew + cy;

        return p;

    }

​

    class Point

    {

        public double X;

        public double Y;

        public string Print(){

            return $"{X},{Y}";

        }

    }

}