// INTEGRATION
// Program 14 : To impliment Trapezoidal integration formula
// ---------------------------------------------------------

#include <stdio.h>
#include <conio.h>
#include <math.h>

#define F(x) (1.0/(1.0+x*x))

main()
{
	int i, n;
	double a, b, h, x, y = 0.0;
	
	printf(" Enter lower limit  : ");
	scanf("%lf", &a);
	printf(" Enter upper limit  : ");
	scanf("%lf", &b);	
	printf(" Enter number of subintervals : ");
	scanf("%d", &n);
	
	h = (b - a) / (double)(n);
	
	for( i=0, x=a; i<=n ; i++, x+=h)
	{
		if( i == 0 || i == n )
			y += F(x);
		else
			y += 2.0*F(x);
	}
	
	y *= h / 2.0;
	
	printf("\n Value of integration = %.10f", y );
	getch();
}