4_34.cpp

来自「C++程序设计技能百练随书配套光盘的源码」· C++ 代码 · 共 38 行

# include<stdio.h>
# include<math.h>
# include<iostream.h>
double fx(double w);
double integral(double s,double t,int m);

void main()
{
	int n;
	double a,b,I;
	printf("请输入积分区间（从a到b），并输入等分区间数n：\n");
    cin>>a>>b>>n;
    I=integral(a,b,n);
	printf("I=%f\n",I);
}
double fx(double w)
{
	return (log(1.0+w)/(1.0+w*w));
}
double integral(double s,double t,int m)
{
	double (*p)(double w);
	p=fx;
	double f=0.0,h,x,y1,y2,area;
	h=(t-s)/m;
	x=s;
	y1=(*p)(x);
	for(int i=1;i<=m;i++)
	{
		x+=h;
		y2=(*p)(x);
		area=(y1+y2)*h/2;
		y1=y2;
		f+=area;
	}
	return f;
}