/*用do...while 語句計(jì)算平方根的簡易近似算法。該算法一開始猜想一個(gè)較為接近待求的平方根
  _                                                   
√a  的值，初始值不必非常接近；x = a就是非常好的選擇
*/



#include <iostream>
#include <cmath>

using namespace std;

int main()
{ 
	 cout<< "Please enter a number:  ";
	 double a;
	 cin >> a;

	 const double EPSILON = 1E-14;
	 double xnew = a;
	 double xold;

	 do
	 {
		 xold = xnew;
		 xnew = (xold + a / xold) / 2;
	 }
	 while((fabs(xnew - xold) > EPSILON));

	 cout << "The square root is" << xnew << "\n";

	 return 0;
}