template <typename F>
class TrapezoidalRule : public IntegrationMethod<F> {
public:
    double Integrate (const F& func, const double& a, const double& b, const int& n) const override {
        double sum = 0;
        for (auto i = 0; i < n; i++) {
            double x1 = X_n(a, b, n, i);
            double x2 = X_n(a, b, n, i + 1);
            sum += ((func(x1) + func(x2)) / 2) * (x2 - x1);
        }
        return sum;
    }
};