复化辛浦生.cpp

来自「计算方法复化辛浦生求积分,给学习计算方法的同学使用」· C++ 代码 · 共 42 行

#include "iostream.h"
#include "math.h"
#include "iomanip.h"
double Simpson(double a,double b,int n);
double f(double x)
{
    
	if (x<=0.0001) return 1;
	else return sin(x)/x;   
}

int main()
{
  double a,b;
  int n;
  cout<<"输入a"<<endl;
  cin>>a;
  cout<<"输入b"<<endl;
  cin>>b;
  cout<<"输入n"<<endl;
  cin>>n; 
  cout<<setprecision(7)<<Simpson(a,b,n);
  return 0;
}
double Simpson(double a,double b,int n)
{
  double s,x,h;
  h=(b-a)/n;
  x=a;
  s=f(a)-f(b); 
  for (int i=1;i<=n;i++)
  {
	  x=x+h/2;
	  s=s+4*f(x);
      x=x+h/2;
	  s=s+2*f(x);
  }
  s=s*h/6;
  return s;
}