复化求积2.cpp

常用的数值分析算法

#include<iostream.h>
#include<Math.h>
#define a 0
#define b 3.1415926535897932

double Hxun(double A,double H,int N)
{
  double hres=0.0;
  double hxunhuan=0.0;
  for(int i=1;i<=N;i++)
  {
    hxunhuan=hxunhuan+exp(A+((2*i-1)*H)/2)*cos(A+((2*i-1)*H)/2);
  }
   hres=H*hxunhuan;
   return hres;
}

double T1n(double A,double B,double H,int N)
{ double res=0.0;
  double pas=0.0; 
  for(int k=1;k<N;k++)
  {
     pas=pas+exp(A+k*H)*cos(A+k*H);
  }
     res=(H/2)*(exp(A)*cos(A)+2*pas+exp(B)*cos(B));
     return  res;
} 

double T2n(double A,double B,double H,int N)
{    double tzhi=0.0,hzhi=0.0,final=0.0;
	 tzhi=T1n(A,B,H,N);
     hzhi=Hxun(A,H,N);
     final = (tzhi+hzhi)/2;
     return final;
}

void main()
{ double h,comp=1.0;
  double result1=0.0;
  double result2=0.0;
  int n=1;
  h=b-a;
 while(1)
  {
	 result1=T1n(a,b,h,n);
	
     result2=T2n(a,b,h,n);
	
	 comp=result2-result1;
	 
	 if((comp<pow(10,-6)))
		 break;
	 else
	     n=2*n;
	     h=h/2;
	
  }
  cout<<"the result is:"<<result2<<" "<<n<<endl;


}