Ряд тейлора при помоши do while

#include<iostream>
#include<math.h>
using namespace std;
int main()
{
    double epsilon = 1e-006;
    double x = -1;
    do { cout << "Input x ( 0<x<2 ) = "; cin >> x; } while (x > 0 && x < 2);
 
    double sum = 0;
    int n = 1;
    while ()
    {
        
    }
 
    cout << "\nresult is " << sum << " (+- " << epsilon << ")" << endl;
    cout << "Numer of last added member is " << n << endl;
    system("pause");
    return 0;
}
}

#include<iostream>
#include<math.h>
using namespace std;
 
int main()
{
    double epsilon = 1e-006;
    double x = -1;
    do { cout << "Input x ( 0<x<=2 ) = "; 
    cin >> x; 
    } 
    while (x <= 0 || x > 2);
 
    double sum = 0;
    int n = 1;
    while (fabs(pow(-1, n)*pow(x - 1, n + 1) / (n + 1)) > epsilon)
    {
        sum += pow(-1, n)* pow(x - 1, n + 1) / (n + 1);
        n++;
    }
 
    cout << "\nresult is " << sum << " (+- " << epsilon << ")" << endl;
    cout << "Numer of last added member is " << n << endl;
    system("pause");
    return 0;
}

#include <iostream>
#include <cmath>
using namespace std;
 
int main()
{    
    int n;
    double x, an, S, eps;    
    
    do 
    { 
       cout << "Input x ( 0<x<2 ) = "; cin >> x;
       if (x <= 0 || x >= 2) cout <<"0<x<2 !!! Repeat please...\n";
    } 
    while (x <= 0 || x >= 2);
    
    do
    {
       cout << "Input eps ( 0<eps<1) = "; cin >> eps;
       if (eps<=0 || eps>=1) cout <<"0<eps<1 !!! Repeat please...\n";
    }
    while (eps<=0 || eps>=1);
    
        n=2;
        an=x-1;
        S=0.0;
        do 
        {
            S+=an;            
            an*=-(x-1)*(n-1)/n;            
            n++;               
        }
        while(fabs(an)>=eps);
    cout <<" x      S(x)     ln(x)\n";     
    cout <<x<<"  "<<S<<"  "<<log(x)<<endl;      
    
system("pause");
return 0;
}