Pole pewnego koła

public class Test
{
    static void Main(string[] args)
        {
            string tekst = Console.ReadLine();
            string[] tab = tekst.Split(' ');
            double r = double.Parse(tab[0]);
            double d = double.Parse(tab[1]);
            Console.WriteLine(ObliczPole(r, d).ToString().Replace(',','.'));
            Console.ReadKey();
        }

        private static double ObliczPole(double r, double d)
        {
            double pi = 3.141592654;
            double wynik = -1 * ((d / 2) * (d / 2) - r * r);
            return Math.Round(pi * wynik, 2);
        }
}