Вычислительная математика. Урок 3. Проверим ряд Фурье при помощи программы на C#.

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Text;

using System.Windows.Forms;

namespace WindowsFormsApplication1

{

    public partial class Form1 : Form

    {

        List<double> a;

        List<double> b;

        public Form1()

        {

            InitializeComponent();

        }

        private double fun(double x, int cn)

        {

            double res=-Math.PI/2;

            for(int i=1; i<=cn; i++)

            {

                res=res+a[i-1]*Math.Cos(x*i)+b[i-1]*Math.Sin(x*i);

            }

            return res;

        }

        private void button1_Click(object sender, EventArgs e)

        {

            a = new List<double>();

            b = new List<double>();

            int cn = 10;

            for (int i = 1; i <= cn; i++)

            {

                double i_d=Convert.ToDouble(i);

                a.Add(2/Math.PI/i_d/i_d*(1-Math.Pow(-1,i_d)));

                b.Add(2/i_d*(Math.Pow(-1,i_d+1)));

            }

            StringBuilder sb = new StringBuilder();

            for (int j = 0; j <= 100; j++)

            {

                double x = -Math.PI + j * 0.1;

                sb.AppendFormat("{0}; {1}\n", x,fun(x,cn));

            }

            System.IO.File.WriteAllText("c:\\3\\fur.txt", sb.ToString());

        }

    }

}