C语言如何使用傅里叶展开式计算圆周率PI

这段代码通过傅里叶展开式计算圆周率

具体公式为：π=∑(-1)^n/(2n-1)

#include <iostream>
#include <math.h>

using namespace std;

int main(){
        long double pi = 0;
        long double n = 1, x = 1;
        int sign = 1;

        while ( fabs(x) > 1e-8){

                pi = pi + 4*x;
                n++;
                sign = sign * (-1);
                x = sign / double(2*n-1);
        }

        cout << "the value of pi is : " << pi << "\n" << endl;

        return 0;
}

测试结果为：

the value of pi is : 3.14159