Программа:

#include
#include

using namespace std;

double f(double a, double b, double c) {
    return sin(a) * sin(b) * sin(c);
}

int main() {
    double a, b, c;
    cout << "a = ";
    cin >> a;
    cout << "b = ";
    cin >> b;
    cout << "c = ";
    cin >> c;
    cout << "x = " << pow(f(a, b, c), 2) + pow(f(a, b, c), 3) << endl;
    return 0;
}