/* simpson's (1/3) Rule */
#include<stdio.h>
#include<conio.h>
#include<math.h>
void main ( )
{
  float f (float x); /* function prototype */
  float a, b , h, sum = 0.0 , result;
  int i , n;
  clrscr ();
  printf(" Enter lower limit of the integral:");
  scanf("%f", &a);
  printf("\n Enter upper limit of the intgral :");
  scanf("%f" , &b);
  printf("\n Enter the number of segments:");
  scanf("%d", &n);

  if(n % 2!= 0)
   printf("\n Number of segments not even number\n");
  else
{
  h=(b-a)/n;
  sum =f(a)+f(b); /*Function call */
  for(i=1; i<n; i++)
{
  if(i %2 ==0)
   sum = sum +2.0*f(a+i*h);/*function call*/
  else
   sum = sum + 4.0*f(a+i*h);/*function call*/  
}
  result =(h/3.0)* sum;
  printf("\n\ Value of integral is = %f\n\n ", result );
}
  getch( );
}
  /* function definition f( )*/
  float f ( float x)
{
  return(1.0/(1.0 + x*x)); /* integrand */
}