用辛普生法對幾個不同的被積函式求指定區間的定積分。被積函式為f(x)，積分割槽間[a,b]被等分為n=2k份，每份步長為h=(b-a)/n，則積分值為：S≈h((f(a)+f(b))/2 +f(a+h)+…+f(a+(n-1)h))。

執行結果：

//辛普森法求積分
copyright vivi_and_qiao 李偉
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace 辛普森法求積分
{
    delegate
 
 double MyDelegate(double x);
    class Function
    {
        public double f1(double x)
        {
            return x * x;
        }
        public string getf1()
        {
           return "y= x* x";
        }
        public double f2(double x)
        {
            return 2 * x + 1;

        }
        public
 
 string getf2()
        {
            return "y=2 * x + 1";
        }
        public double f3(double x)
        {
            return Math.Atan(x);

        }
        public string getf3()
        {
            return "y= Math.Atan(x)";
        }
        public double f4(double x)
        {
            return
 
 Math.Exp(Math.Exp(x));

        }
        public string getf4()
        {
            return "y=Math.Exp(Math.Exp(x))";
        }
    }
    class Program
    {
        public static double jifen(double a,double b,int n ,MyDelegate my)
        {
            double h = (b - a)/n;
            double value=0;
            for (int i = 1; i <= n; i++)
                value += h * (my(a + (i - 1) * h));
            return value;
        }
        static void Main(string[] args)
        {
            int n;
            double a, b;
            Console.WriteLine("請輸入精度！");
            n = int.Parse(Console.ReadLine());
            Console.WriteLine("請輸入積分上限");
            a = int.Parse(Console.ReadLine());
            Console.WriteLine("請輸入積分下限！");
            b = int.Parse(Console.ReadLine());
            Function f=new Function();
            MyDelegate my=f.f1;
            Console.WriteLine("函式："+f.getf1()+"在積分割槽間："+"["+a+","+b+"]"+"的積分值為："+jifen(a,b,n,my));
            my = f.f2;
            Console.WriteLine("函式：" + f.getf2() + "在積分割槽間：" + "[" + a + "," +b+ "]" + "的積分值為：" + jifen(a, b, n, my));
             my = f.f3;
            Console.WriteLine("函式：" + f.getf3() + "在積分割槽間：" + "[" + a + "," +b+ "]" + "的積分值為：" + jifen(a, b, n, my));
            my = f.f4;
            Console.WriteLine("函式：" + f.getf4() + "在積分割槽間：" + "[" + a + "," +b+ "]" + "的積分值為：" + jifen(a, b, n, my));
            Console.ReadKey();
        }
    }
}