/*写一个用矩阵法求定积分的通用函数，分别求sinx,cosx,exp(x)的定积分*/

#include <stdio.h>
#include <math.h>
#define N 1000

int main()
{
	int fun1(double m,double n,double *sum);
	int fun2(double m,double n,double *sum);
	int fun3(double m,double n,double *sum);
	double m,n;
	double an; 
	double *sum = &an;
	
	printf("请输入定积分的上下限：\n");
	scanf("%lf %lf",&m,&n);
	
	fun1(m,n,sum);
	printf("sinx的定积分是%lf\n",an);
	
    fun2(m,n,sum);
	printf("cosx的定积分是%lf\n",an);
	
	fun3(m,n,sum);
	printf("exp(x)的定积分是%lf\n",an); 
	
 }
 
//sinx的定积分函数 
int fun1(double m,double n,double *sum)
{
	double ran;
	double i;
	
	ran = fabs(m - n) / N; 
	*sum = 0.0;
	for(i = n;i < m;i = i + ran)
	{
		*sum = *sum + (sin(i) * ran);
	}
 } 
 
//cosx的定积分函数 
int fun2(double m,double n,double *sum)
{
	double ran;
	double i;
	
	ran = fabs(m - n) / N; 
	*sum = 0.0;
	for(i = n;i < m;i = i + ran)
	{
		*sum = *sum + (cos(i) * ran);
	}
} 

//exp(x)的定积分函数 
int fun3(double m,double n,double *sum)
{
	double ran;
	double i;
	
	ran = fabs(m - n) / N; 
	*sum = 0.0;
	for(i = n;i < m;i = i + ran)
	{
		*sum = *sum + (exp(i) * ran);
	}
} 

谭浩强C程序设计（第四版）p292第13题
指针真是烦！！！！
一开始看到矩阵法我还奇怪，后来发现就是我学的微元法。
数据类型也很烦！！！！！