0

ok so I was doing a a function that would find the square root of a number to a certain precision using newtons method and this is what I came up with

```
/*
* File: main.cpp
*
*
* Created on July 6, 2012, 6:58 PM
*/
#include <iostream>
#include <cstdlib>
using namespace std;
/*
*
*/
double sqrt(double n)
{
if(n == 0 || n == 1) return n ;
double pres = 0.0001 ;
double x_0 = n/4 ;
double x_1 = x_0- (((x_0*x_0)-n)/(2*x_0)) ;
while(( x_1 - x_0 > pres )){
x_0 = x_1 ;
x_1 = x_0- (((x_0*x_0)-n)/(2*x_0)) ;
}
return x_1 ;
}
int main(int argc, char** argv) {
for(int i = 1 ; i < 15 ; i++){
double z = i*i ;
cout<<"sqrt["<<i*i<<"] = "<<sqrt(z) << endl ;
}
return 0;
}
```

and it would give me the wrong answers so after doing some research I found out that by changing the while loop condition to:

```
while(( x_1 - x_0 > pres || x_1 - x_0 < -0.0001 ))
```

it fixed it and gave me the correct answers

so my question is why do I need the

```
|| x_1 - x_0 < -0.0001
```

in the while loop ?

*Edited 4 Years Ago by rockerjhr*