#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define endl '\n'
#define boostIO() ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
ll gcd(ll a, ll b) { return (b == 0 ? a : gcd(b, a % b)); }

double f(double x) {
    return x + 1 / x - 4 * cos(x);
}

signed main() {
    double l = 0.2, r = 0.5;
    cout << "l = " << l << endl;
    cout << "r = " << r << endl;

    int k = 1;
    vector<double> epss = { 1e-2, 1e-3, 1e-4 };
    double a = l, b = r;
    for (auto eps : epss) {
        cout.unsetf(ios_base::fixed);
        cout << endl << "current epsilon: " << eps << endl;
        cout << fixed << setprecision(5);
        while (true) {
            if (fabs(f(b)) < eps) break;
            a = b - (b - a) * f(b) / (f(b) - f(a));
            b = a - (a - b) * f(a) / (f(a) - f(b));
            cout << "x" << k << " = " << setw(8) << b <<
                "   f(x" << k++ << ") = " << setw(8) << f(b) << endl;


        }
    }
}