// Example 4-7：求π的近似值
#include <iostream.h>
#include <math.h>
void main()
{
	int s = 1;
	double n = 1.0, u = 1.0, pi = 0.0;
	while(fabs(u)>=1e-4)
	{
		pi = pi+u;
		n = n+2;
		s = -s;
		u = s/n;
	}
	cout << "pi = " << 4*pi << endl;
}