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

冷不防 2023-07-25 09:01 28阅读 0赞

/*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！！！！！