C Code for Trapezoidal Rule

#include <stdio.h>

#include <conio.h>

#include <math.h>

float f(float x)

{

  return (exp(x)); //f(x)=exp(x);

}

void main()

{

  float a,b,h,x,sum=0;

  int n;

  printf("Enter a and b: ");

  scanf("%f%f",&a,&b);

  printf("Here, n=1 for Trapezoidal rule");  printf("\nn>1 for Composite Trapezoidal rule\n");

  printf("So, Enter n: ");

  scanf("%d",&n);

  h=(b-a)/n;

  for(x=a;x<=b;x=x+h)

  {

    if(x==a)

      sum=sum+f(x);

    else if(x==b)

      sum=sum+f(x);

    else

      sum=sum+2*f(x);

  }

  sum=h/2*sum;

  printf("\nI=%f",sum);

  getch();

}

OUTPUT:

Simpson's 1/3 Rule >>