lagu.cpp

来自「大量数值计算的算法」· C++ 代码 · 共 21 行

#include<stdio.h>
#include<math.h>
#define PI 3.14159265
 main()
{	
	double x[5]={0,PI/6,PI/4,PI/3,PI/2};
    double f[5]={0,0.5,sqrt(2.0)/2.0,sqrt(3.0)/2.0,1};
	int i,j;
	double sum=0,s,u=PI/12;
	for(j=0;j<5;j++)
	{	s=1;
		for(i=0;i<5;i++)
		{	if(i==j)
				continue;
			else
				s=s*((u-x[i])/(x[j]-x[i]));
		}
		sum+=s*f[j];
	}
	printf("sum=%1.16f\n",sum);
}