// methodHord.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <cmath>


using namespace std;

double f(double x)
{
    // [-1, 1] - отрезок на котором ищем корень
    return 3 * x - cos(x) -1;
    //return sqrt(x) - 2;
}

double first_derivate(double x)
{
    double h = 0.01; // шаг производной
    return (f(x) - f(x - h)) / h;
}

double second_derivative(double x)
{
    double h = 0.01; // шаг производной
    return (f(x + h) - 2 * f(x) + f(x - h)) / (h * h); // вторая производная
}
double methodHord(double(*funct)(double), int a, int b, double eps)
{
    double c;
    double xNext;
    double x0;
    cout << "\t\t" << f(a) * second_derivative(a) << endl;
    cout << "\t\t" << f(b) * second_derivative(b) << endl;
    if (f(a) * second_derivative(a) > 0)
    {
        c = a;
        x0 = b;
        //cout << "c>>> " << c  << endl;
    }
    else if (f(b) * second_derivative(b) > 0)
    {
        c = b;
        x0 = a;
        //cout << "c>>> " << c << endl;
    }
    xNext = x0 + (c - x0) / (1 - f(c) / f(x0));
    while (fabs(xNext - x0) <= eps)
    {
        x0 = xNext;
        xNext = x0 + (c - x0) / (1 - f(c) / f(x0));
    }
    return xNext;
}


int main()
{
    setlocale(LC_ALL, "Russian");
    //cout << "Вторая производная >>> " << second_derivative(20) << endl;
    int a, b;
    cout << "Начало отрезка (a) \n>>> ";
    cin >> a;
    cout << "Конец отрезка (b) \n>>> ";
    cin >> b;
    double eps = 0.00001;
    double m1 = fabs(first_derivate(a)), M1 = fabs(first_derivate(a));
    int sec_a = a;
    for (sec_a; sec_a <= b; sec_a++)
    {
        if (m1 > fabs(first_derivate(sec_a)))
        {
            m1 = fabs(first_derivate(sec_a));
        }
        if (M1 < fabs(first_derivate(sec_a)))
        {
            M1 = fabs(first_derivate(sec_a));
        }
    }
    //cout << m1 << endl << M1 << endl;

    if (M1 <= 2 * m1)
    {
    double res = methodHord(f, a, b, eps);
    cout << res << endl;
    cout << f(res) << endl;
    }
    system("pause");
}