cos recursion

cos.cs

using System;

namespace cos_recursion
{
    class Program
    {
        public static double power(double x, double n)
        {
            if (n == 0)
            {
                return 1;
            }
            else
            {
               return x * power(x, n - 1);
            }
        }

        public static double factorial(double n)
        {
            if(n <=1 )
            {
                return 1;
            }
            else
            {
                return n * factorial(n - 1);
            }
        }

        public static double cosinus(double x, double n)
        {
            if (n == 0)
            {
                return 1;
            }
            else
            {
                return (power(-1, n) / factorial(2 * n)) * power(x, 2 * n) + cosinus(x, n - 1);
            }
        }
        static void Main(string[] args)
        {
            Console.WriteLine(cosinus(0.3,10));
            Console.WriteLine(Math.Cos(0.3));
            Console.ReadLine();
        }
    }
}