matko boska jaka dokladnosc, jogut złoty 1,27!

#include <iostream>
#include <fstream>
#define _USE_MATH_DEFINES
#include <cmath>
#include <stack>
#define M_PI_2     1.57079632679489661923

using namespace std;

int sgn(long double x)
{
    if(x>0)
        return 1;
    else
        return -1;
}

void licz_double(long double x, long double epsilon)
{
    if(x <= 1 && x >= (-1))
    {
        long double suma = x;
        long double potega = x;
        bool p = 0;
        long double nastepny = 1000.0;
        stack<long double> stos_sum;
        stos_sum.push(suma);
        for(int n = 1; nastepny >= epsilon; n+=1)
        {
            potega = potega * x * x;

            if(p==1)
            {
                suma = suma + (potega/(2*n + 1.0));
                stos_sum.push(potega/(2*n + 1.0));
            }
            else
            {
                suma = suma - (potega/(2*n + 1.0));
                stos_sum.push(-potega/(2*n + 1.0));
            }
            p = !p;
            nastepny = ((potega*x*x)/(2*(n+1) + 1.0));


        }
        long double arctan = atan(x);
        long double wynik =0.0;
        int size = stos_sum.size();
        for(int i=0; i <size; i++)
        {
            wynik = wynik + stos_sum.top();
            stos_sum.pop();
        }
        cout << "kolejnosc dodawania od najmniejszych do najwiekszych\n";
        cout << "argument:\t"<< x << "\n";
        cout << "wynik obliczen:\t"<< wynik << "\n";
        cout << "wynik atan stl:\t"<< arctan << "\n";
        cout << "blad wzgledny:\t" << (wynik-arctan)/arctan << "\n\n";
        cout << "kolejnosc dodawania od najwiekszych do najmniejszych\n";
        cout << x << "\t" << suma << "\t" << arctan << "\t" << (suma-arctan)/arctan << "\n\n";
        //cout << x << "\n";

    }
    else
    {
        long double suma = (sgn(x) * M_PI_2) - (1/x);
        long double potega = x;
        bool p = 1;

        for(int n =1; n<1000; n+=1)
        {
            potega = potega * x *x;
            if(p==1)
                suma = suma + 1/((2*n + 1)*potega);
            else
                suma = suma - 1/((2*n + 1)*potega);
            p = !p;
        }
        long double arctan = atan(x);
        cout << x << "\t" << suma << "\t" << arctan << "\t" << (suma-arctan)/arctan << "\n" << fixed;
        //cout << x << "\n";
    }
}

void licz_float(float x, long double epsilon)
{
    if(x <= 1 && x >= (-1))
    {
        float suma = x;
        float potega = x;
        bool p = 0;
        long double nastepny = 1000.0;
        for(int n = 1; nastepny >= epsilon; n+=1)
        {
            potega = potega * x * x;

            if(p==1)
                suma = suma + (potega/(2*n + 1.0));
            else
                suma = suma - (potega/(2*n + 1.0));
            p = !p;
            nastepny = ((potega*x*x)/(2*(n+1) + 1.0));

        }
        float arctan = atan(x);
        cout << x << "\t" << suma << "\t" << arctan << "\t" << fabs((suma-arctan)/arctan) << "\n" << fixed;
        //cout << x << "\n";
    }
    else
    {
        float suma = (sgn(x) * M_PI_2) - (1/x);
        float potega = x;
        bool p = 1;

        for(float n =1.0; n<1000.0; n+=1.0)
        {
            potega = potega * x *x;
            if(p==1)
                suma = suma + 1/((2*n + 1)*potega);
            else
                suma = suma - 1/((2*n + 1)*potega);
            p = !p;
        }
        long double arctan = atan(x);
        cout << x <<"\t" << suma << "\t" << arctan << "\t" << fabs((suma-arctan)/arctan) << "\n" << fixed;
        //cout << x << "\n";
    }
}


int main()
{
    cout << fixed;
    long double x=0;
    long double epsilon=0;
    cout.precision(30);
    cout << "arctg z zadana dokladnoscia\n";
    cout << "podaj argument funkcji\n";

    cin >> x;
    cout << "podaj zadana dokladnosc\n";
    cin >> epsilon;

    licz_double(x, epsilon);
    //licz_float((float)x,epsilon);

    return 0;
}