Trapezodial

 #include <iostream>

#include <math.h>

using namespace std;

float f(float x)

{

    return (1/(1+x*x));

}

int main()

{

    int i,n;

    float x0,xn,h,sum,sum1;

    cout<<"Enter no of intervals: ";

    cin>>n;

    cout<<"Enter x0 & xn: ";

    cin>>x0>>xn;

    h = (xn-x0)/n;

    cout<<"\n h = "<<h;

    sum = f(x0)+f(xn);

    for(i = 1;i<n;i++)

    {

        sum1 = sum1 + 2*f(x0+i*h);

    }

    sum1 = 0.5*h * (sum + sum1);

        cout<<"\nIntegral Value = "<<sum1;

    return 0;

}