#include<iostream>
using namespace std;
void ans(int n)
{
cout<<n<<":";
double pi = 1.0;
for(int i = 1; i <= n; i++)
{
double x = (2.0 * i) / (2.0 * i - 1);
double y = (2.0 * i) / (2.0 * i + 1);
double z = x * y;
pi *= z;
}
cout<<2.0 * pi<<endl;
}
int main()
{
ans(10);
ans(100);
ans(1000);
return 0;
}
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/4bed2e738bd4b31c43adedc185d6277f9e2ff833?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
追问亲,为什么要用using namespace啊?如果我用三个while语句分别令n=10、100、1000是不是就可以不用namespace啊~(初学菜鸟别见笑)
追答C++输入(cin)输出(cout)包含在using namespace里面,没什么可讲的。