程序基本算法习题解析 求pi的近似值

思路：

pi/4 = 1 - 1/3 +1/5 -1/7 + ...

附上代码： 

// Chapter5_3.cpp : Defines the entry point for the application.
// 求pi的近似值

#include "stdafx.h"
#include<iostream>
#include<math.h>
using namespace std;

int main()
{
	float sum = 1,pi,last = 1,fenzi = 1,fenmu = 1;
	while(last >= 1e-6)
	{
		fenzi = -fenzi;
		fenmu = fenmu + 2;
		sum = sum + fenzi/fenmu;
		last = 1/fenmu;
	}
	pi = sum*4.0;
	cout << "pi = " << pi << endl;
	system("pause");
	return 0;
}

运行结果：