C++简单练习题1——求π

#include <iostream>//#include <math.h>using namespace std;double arctan(double x);int main() {double pie;pie = 16.0 * arctan(1 / 5.0) - 4.0 * arctan(1 / 239.0);cout << pie << endl;    return 0;}double arctan(double x){int i = 1;double val = 0.0;int t;while (pow(x, i) / i > (1e-15)){if (i % 4 == 1)   //正负交替处理t = 2;val = val + pow(-1, t) * pow(x, i) / i;i += 2;t = 1;}return val;}