求平方根C++

   求平方根,正根.以前都不會.昨天看數學,看到了,寫了出來.自己又小最佳化了一下,很不錯.

// squareRoot.cpp -- 2011-08-29-01.04#include "stdafx.h"#include <iostream>double squareRoot (double radicand, double precision) ;int _tmain(int argc, _TCHAR* argv[]){std ::cout << squareRoot(9, 0.000001) << std ::endl ;return 0;}double squareRoot (double radicand, double precision){if (radicand > 0){double squareRoot = radicand / 10 ;while (squareRoot * squareRoot > radicand)squareRoot /= 2 ;double fakePrecision = 0.1; while (1){while ((squareRoot + fakePrecision) * (squareRoot + fakePrecision) <= radicand){squareRoot += fakePrecision ;}if (fakePrecision > precision){fakePrecision /= 10 ;}else{return squareRoot ;}}}else{std ::cerr << "Radicand must > 0" << std ::endl ;return 0 ;}}