double newtons_method(double (*func)(double), double n) {
    // Question... where does func(x) = n?
    // func(x) - n = 0
    double f(double x) { return func(x) - n; }

	// initial arbitrary guess
    double guess = 0.5;
    printf("Guess for func(x) - %.2lf = 0\n", n);
    printf("%lf\n", guess);

    for (int i = 0; i < 7; ++i) {
        // update guess for next iteration
        // x_1 = x_0 - f(x_0) / f'(x_0)
        // (x_n+1) = x_n - f(x_n) / f'(x_n)
        guess = guess - (f(guess) / derivative(f, guess));
        printf("%lf\n", guess);
    }
}