Trapezoidal Method by AN Sir

#include <iostream>
#include <cstdlib>

using namespace std;

class Trapezoidal{
    public:
        double function1(double x);
        double trapezoidal(double a, double b, long n);
};

double Trapezoidal::function1(double x){
    double y;
    //y = 4 / (1 + x * x);
    //y = 1 / (1 + x);
    y = x * x * x * x;
    return y;
}

double Trapezoidal::trapezoidal(double a, double b, long n){
    long  i;
    double s1, s2, h, i_trap;
    h = (b - a)/n;
    s1 = function1(a) + function1(b);
    s2 = 0;
    for(i = 1; i < n; i++){
        s2 = s2 + function1(a + i*h);
    }
    i_trap = 0.5 * h * (s1 + 2 * s2);
    cout << "Number of intervals = " << n << endl;
    cout << "Value of integral using Trapezoidal Rule = " << i_trap << endl;
    return i_trap;
}

int main(int argc, char** argv) {
    double a, b, it;
    long n;
    system("cls");
    cout << "Enter lower limit of your integral: ";
    cin >> a;
    cout << "Enter upper limit of your integral: ";
    cin >> b;
    cout << "Enter total number of intervals: ";
    cin >> n;
    Trapezoidal T;
    it = T.trapezoidal(a, b, n);
    cin.ignore();
    cin.get();
    return 0;
}