write a program to integrate a function using trapezoidal rule in c++

write a program to integrate a function using trapezoidal rule in c++.

CODE:
#include<iostream.h>
#include<conio.h>
float f(float x)
{
return(1/(1+x));
}
void main()
{
clrscr();
float h,a,b,sum=0;
int n,i;
cout<<"enter lower limit :" ;
cin>>a;
cout<<"enter upper limit : ";
cin>>b;
cout<<"enter number of intervals : ";
cin>>n;
h=(b-a)/n;
sum=(f(a)+f(b))/2;
for(i=1;i<n;i++)
{
sum=sum+f(a+i*h);
}
sum=sum*h;
cout<<"x\ty"<<endl;
for(i=0;i<=n;i++)
{
cout<<i<<"\t"<<f(a+i*h)<<endl;
}
cout<<"\nvalue of integral using trapezoidal rule: "<<sum;
getch();

}

OUTOUT: