#include <iostream>
#include <cmath>
using namespace std;

double f( double x )
{
   return( x*x + 2*x + 3 );     // Function f(x)
}

int main()
{
   double a, b, h, sum, x;
   short i, n;

   n = 100;    // Number of subintervals
   a = 0.0;    // Lower bound
   b = 2.0;    // Upper bound
 
   h = ( b - a ) / n;
   sum = ( f( a ) + f( b ) ) / 2;
   x = a;
   for( i = 1; i <= n-1; i++ )
   {
      x += h;
      sum += f( x );
   }
   cout << "Trapezoid rule result: " << h * sum << endl;
   
   return( 0 );
}