#include
#include
using namespace std;
int main()
{
double x = 0;
double sum = 0;
double a = 1;
int n;
for (n=1;fabs(x)>1e-8;n++)
{
x = (a) / (2 * n - 1);
sum = sum + x;
a=-a;
}
cout << "Π/4的近似值=" << sum << endl;
}
虽然看不太懂 但应该不会执行for循环里面的，条件似乎不满足
修改如下，供参考：
#include <iostream>
#include <cmath>
using namespace std;
int main()
{
double x = 1.0; //修改
double sum = 0;
double a = 1.0;
int n;
for (n = 1; fabs(x) > 1e-8; n++)
{
x = (a) / (2 * n - 1);
sum = sum + x;
a = -a;
}
cout << "Π/4的近似值=" << sum << endl;
return 0;
}