Trapezoidal Rule

#include<bits/stdc++.h>

using namespace std;

double a, b, x[10], y[10], delX, T_n, result;

void Trapizoidal_rules(double n)
{
    int i;
    delX = (b - a)/n;
    for( i = 0; i <= n; i ++)
    {
        x[i] =  a;
        a += delX;
    }

    for(i = 0; i <= n; i++)
    {
        y[i] = sqrt(1 - x[i]*x[i]);
    }

    for(i = 0; i <= n; i ++)
    {
        if((i ==  0) || (i ==  n))
            T_n += y[i];
        else
            T_n += 2*y[i];
    }

    result = T_n * 0.5 * delX;


}


int main()
{
    double n;
    int j = 1;
    cout<< "Please input the value of n." << endl;
    cin >> n;
    cout <<"Now input the limit(lower limit, upper limit):";
    cin >> a >> b;

    Trapizoidal_rules(n);

        cout << "While n = " <<  n <<  " and result is = " << result  << endl;



    return 0;
}