编程函数解决sin x积分问题

写一个sin x得函数，要求实现从0到1积分
∫（0.1）sin x

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
double a[1001];
void split()
{
for (int i = 0; i < 1001; i++)
{
a[i] = (1.0 / 1000)i;
}
}
void cal_sin()
{
double ret = 0.0;
for (int i = 0; i < 1000; i++)
{
double avg = (a[i] + a[i + 1]) / 2.0;
ret += (sin(avg)(1.0/1000));
}
printf("%lf\n", ret);
}
int main()
{
split();
cal_sin();
system("pause");
return 0;
}