1 #include <iostream>
 2 
 3 /* run this program using the console pauser or add your own getch, system("pause") or input loop */
 4 #include<iomanip>
 5 #include<cmath>
 6 using namespace std;
 7 int main(int argc, char** argv) {
 8     int s=1;
 9     double n=1;
10     double t=1;
11     double pi=0;
12     while((fabs(t))>1e-7)
13     {
14         pi=pi+t;
15         n=n+2;
16         s=-s;
17         t=s/n;
18     }
19     pi=pi*4;
20     cout <<"pi="<<setiosflags(ios::fixed)<<setprecision(6)<<pi<<endl;
21     return 0;
22 }