用C语言写定积分的通用函数：sin(x),cos(x),eX.

#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);
}