klikaa

Take sqrt() only from positive numbers.. So use fabs()/abs() or equivalent code, to get rid of negatives...

BTW, y[] is defined as float, so complex class sqrt() is never executed, only regular one.

thanks for you help... i figured it out.. now its all working

sqrt() the most likely is returning NaN (Not A Number) for negative input.

The same happens with regular hand calculators (E letter appears etc.)

 

http://en.wikipedia.org/wiki/NaN

It's mentioned on wiki page

"There are three kinds of operations that can return NaN:

[...]

The square root of a negative number."

and how can i change that? that i doesn't give nan ?

The part

for(int i=1; i<n; i++)
{
x=sqrt(y*i);
cout<<"x"<<i<<": "<<x<<endl;
}

isn't working wll, for some elements the result is non, i thought that i because the numbers are complex, but not with include complex i get the same resut.. can anyone help me

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

int main()
{
    int n,elem[20];
    float y[20],A[20];
    complex<float>  x[20];
    
    cout<<"Number of elements?"<<endl;
    cin>>n;
    cout<<"Insert elements:"<<endl;
    for(int i=0; i<n; i++)
    {
        cin>>elem[i];
        
    }
    
    
    A[0]=pow(elem[0],2);
    
    for(int j=1; j<n; j++)
    {
        A[j]=pow(elem[j],2);
    
            int i=1;
            while((i+j)<=n-1&&(i<=j))
            {
                
                A[j]=A[j]+pow((-1),i)*2*(elem[j-i]*elem[j+i]);
                i=i+1;
            
            }
    

            cout<<"A"<<j<<":"<<A[j]<<endl;
    
    
    }
    
    for(int i=1; i<n; i++)
    {
        y[i]=A[i]/-A[i-1];
        cout<<"y"<<i<<": "<<y[i]<<endl;
    }
    
    for(int i=1; i<n; i++)
    {
        x[i]=sqrt(y[i]*i);
        cout<<"x"<<i<<": "<<x[i]<<endl;
    }

}

thanks, that was the problem ))

So i have to write a c++ program for the Graeffe's square root method
I have am stuck here when i have this formula transform into c++ code, the formula is on the link

The code works particulary, the (elem[j-1]*elem[j+i]) doesn't work, it's beeing ignored and i don't know why... can any one help me?

http://latex.codecogs.com/gif.latex?A_{k}=a_{k}^{2}+2\sum_{s=1}^{k}(-1)^{s}a_{k-s}*a_{k+s},&space;k=0,....n

cout<<"How many elements?"<<endl;
cin>>n;
cout<<"Insert x:"<<endl;
for(int i=0; i<n; i++)
{
cin>>elem;

}


C[0]=pow(elem[0],2);

for(int j=1; j<n; j++)
{
C[j]=pow(elem[j],2);

int i=1;
while((i+j)<=n-1&&(i<=j))
{

C[j]=C[j]+(-1)^i*2*(elem[j-1]*elem[j+i]);
i=i+1;

}


cout<<"C"<<j<<":"<<C[j]<<endl;

}