用C语言写定积分的通用函数：sin(x),cos(x),eX.

[code]#include<stdio.h>
/************************************************************/
/*sin,cos,exp函数已经存在于系统的数学函数库中，程序开头需要定义math头文件*/
/************************************************************/
#include<math.h>
/****************主函数**************************************/
int main()
{
float integral(float(*)(float), float, float, int);
float fsin(float);
float fcos(float);
float fexp(float);
float a1, b1, a2, b2, a3, b3, c, (*p)(float);//定义一个float类型的指针
int n = 20;
//输入积分上下限
printf("enter a1,b1:\n");
scanf("%f%f", &a1, &b1);
printf("enter a2,b2:\n");
scanf("%f%f", &a2, &b2);
printf("enter a3,b3:\n");
scanf("%f%f", &a3, &b3);

p = fsin;//用float型指针指向fsin函数
c = integral(p, a1, b1, n);
printf("sin(x)=%f\n", c);

p = fcos;//用float型指针指向fcos函数
c = integral(p, a2, b2, n);
printf("cos(x)=%f\n", c);

p = fexp;//用float型指针指向exp函数
c = integral(p, a3, b3, n);
printf("exp(x)=%f\n", c);
return 0;
}
float integral(float(*p)(float), float a, float b, int n)
{
int i;
float x, h, s;
h = (b - a) / n;//牛顿莱布尼茨公式运用
x = a;
s = 0;
for (i = 0; i < n; i++)
{
x = x + h;
s = s + (*p)(x)*h;
}
return (s);
}
float fsin(float x)
{
return sin(x);
}
float fcos(float x)
{
return cos(x);
}
float fexp(float x)
{
return exp(x);
}