>>571
#include <stdio.h>
#include <math.h>
double f(double x)
{
return x * exp(x);
}
int main()
{
int i, n;
double x, dx, sum = 0;
printf("n = ");
scanf("%d", &n);
dx = 1.0 / n;
for (i = 0;i < n; i++) {
x = (double)i / n;
sum += (f(x) + f(x + dx)) * dx / 2.0;
}
printf("result = %f\n", sum);
}
結果が正しいか確認してません