#include <iostream>
using namespace std;

double fff(double x, int a, double Pi)
{
    double fx;
    fx = a*x - pow(cos(Pi*x), 2);
    return fx;
}

double fun(int a, int& k_iter)
{
    double Pi = 3.14159265, fa, fx, e = pow(10, (-6)), x, Sa = 0.2, Sb = 0.8;
    k_iter = 0;
    fa = a*Sa - pow(cos(Pi*Sa), 2);
    do
    {
        x = (Sa + Sb) / 2;
        fff(x, a, Pi);
        if (fff(x, a, Pi)*fa <= 0) Sb = x;
        else Sa = x;
        k_iter++;
    } while (abs(Sa - Sb) > 2 * e);
    return x;
}

int main( )
{
    double Pi = 3.14159265;
    int a, Kiter;
    for (a = 1; a <= 3; a++)
    {
        fun(a, Kiter);
        int *pk = &Kiter;
        if (a == 2) cout << "a=" << a << "   x=" << fun(a, Kiter) << "       f(x)=" << a*fun(a, Kiter) - pow(cos(Pi*fun(a, Kiter)), 2) << "   k_iter=" << *pk << '\n';
        else cout << "a=" << a << "   x=" << fun(a, Kiter) << "   f(x)=" << a*fun(a, Kiter) - pow(cos(Pi*fun(a, Kiter)), 2) << "   k_iter=" << *pk << '\n';
    }
    system("pause");
    return 0;
}