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# Thread: Help with understanding what his algorithm does and how it comes up with the numbers

1. Junior Member
Join Date
Oct 2012
Posts
1

## Help with understanding what his algorithm does and how it comes up with the numbers

Just starting to lean about algorithm and programming and professor gave us this question and told us to figure out what i does thanks for the help
Code:
```#include <cstdlib>
#include <iostream>
#include <cmath>
using namespace std;
int main( )
{
double a, x_old, x_new;
cout << "Enter a positive DECIMAL number => ";
cin >> a;
x_old = 1;
x_new = 0.5*( 1 + a );
while( fabs(x_old - x_new) >= 0.00005)
{
x_old = x_new;
x_new = 0.5*( x_old * x_old + a )/x_old;
}
cout << "\nThe value that you are seeking is " << x_new << endl;
cout << "Press the enter key to continue ...";
cin.get();
return 0;
}```
Last edited by cilu; October 2nd, 2012 at 04:36 AM. Reason: code tags

2. Elite Member Power Poster
Join Date
Apr 1999
Posts
27,449

## Re: Help with understanding what his algorithm does and how it comes up with the numb

Originally Posted by soldatik21
Just starting to lean about algorithm and programming and professor gave us this question and told us to figure out what i does thanks for the help
OK, so what's your question?

Regards,

Paul McKenzie

3. Elite Member Power Poster
Join Date
Nov 2003
Location
Florida
Posts
12,518

## Re: Help with understanding what his algorithm does and how it comes up with the numb

Originally Posted by soldatik21
Just starting to lean about algorithm and programming and professor gave us this question and told us to figure out what i does thanks for the help
Then you should probably do what your professor asked you to do. This isn't the do my homework for me forum.

5. Member +
Join Date
Jan 2009
Posts
596

## Re: Help with understanding what his algorithm does and how it comes up with the numb

As a first step, ignore the actual code and just try running it. See what output you get for various input values. Then, try to guess what function the code is calculating (it should be fairly obvious).
Once you have an idea as to what function this code calculates, see if you can work out how it is doing it.

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