using System;

public class Program
{
    public static void Main(string[] args)
    {
        double a = 0;
        double b = 2.5;
        double c = -0.2;
        int n = 0;
        double e1 = 0.001;
        double xn1 = 0;
        double xn = 2.5;

        if (xn >= a && xn <= b)
        {
            while (true)
            {
                xn1 = xn + c * (2 * xn - 4 * Math.Cos(xn) - 0.6);
                n++;
                Console.WriteLine($"{n} : {xn}");
                if (Math.Abs(xn1 - xn) <= e1 && Math.Abs(xn1 - xn) <= e1)
                {
                    break;
                }

                xn = xn1;
            }
            Console.WriteLine("n = {0} ", n);
            Console.WriteLine("xn1 = {0} ", xn1);
        }
        else
        {
            Console.WriteLine("Введенное число не принадлежит отрезку!");
        }


        Main2();
        Main3();
        Console.ReadLine();
    }


    public static void Main2()
    {
        double a = 0;
        double b = 2.5;
        int n = 0;
        double e1 = 0.001;
        double xn1 = 0;
        double xn = 2.5;
        if (xn >= a && xn <= b)
        {
            while (true)
            {
                xn1 = xn - (2 * xn - 4 * Math.Cos(xn) - 0.6) / (2 + 4 * Math.Cos(xn));
                n++;
                if (Math.Abs(xn1 - xn) <= e1 && Math.Abs(xn1 - xn) <= e1)
                {
                    break;
                }
                else
                {
                    xn = xn1;
                }
            }
            Console.WriteLine("n = {0} ", n);
            Console.WriteLine("xn1 = {0} ", xn1);
        }
        else
        {
            Console.WriteLine("Введенное число не принадлежит отрезку!");
        }
    }

    public static void Main3()
    {
        double a = 0;
        double b = 2.5;
        double c = -0.2;
        int n = 0;
        double e1 = 0.001;
        double xn1 = 0;
        double xn = 2.5;

        double x0 = 2 + 4 * Math.Cos(xn);
        if (xn >= a && xn <= b)
        {
            while (true)
            {
                xn1 = xn - (2 * xn - 4 * Math.Cos(xn) - 0.6) / x0;
                n++;
                if (Math.Abs(xn1 - xn) <= e1 && Math.Abs(xn1 - xn) <= e1)
                {
                    break;
                }
                else
                {
                    xn = xn1;
                }
            }
            Console.WriteLine("n = {0} ", n);
            Console.WriteLine("xn1 = {0} ", xn1);
        }
        else
        {
            Console.WriteLine("Введенное число не принадлежит отрезку!");
        }
    }
}