---

#include <iostream>
#include <cmath>
#include <clocale>
using namespace std;

int main() {
    setlocale(LC_ALL, "Russian");

    double a, b, c, x, t2;

    cout << "Введите a, b, c, x: ";
    cin >> a >> b >> c >> x;

    t2 = (1.0 / (2 * a * b)) *
         log((sqrt(c * c - b * b) * tan(a * x) + 2) /
             (sqrt(c * c - b * b) * tan(a * x) - 2));

    cout << "Результат t2 = " << t2 << endl;

    return 0;
}