c program to implement numerical integration using trapezoidal rule

 

Numerical Integration Using Trapezoidal Method C Program

#include<stdio.h>

#include<conio.h>

#include<math.h>

/* Define function here */

#define f(x) 1/(1+pow(x,2))

int main()

{

 float lower, upper, integration=0.0, stepSize, k;

 int i, subInterval;

 

 /* Input */

 printf("Enter lower limit of integration: ");

 scanf("%f", &lower);

 printf("Enter upper limit of integration: ");

 scanf("%f", &upper);

 printf("Enter number of sub intervals: ");

 scanf("%d", &subInterval);

 /* Calculation */

 /* Finding step size */

 stepSize = (upper - lower)/subInterval;

 /* Finding Integration Value */

 integration = f(lower) + f(upper);

 for(i=1; i<= subInterval-1; i++)

 {

  k = lower + i*stepSize;

  integration = integration + 2 * f(k);

 }

 integration = integration * stepSize/2;

 printf("\nRequired value of integration is: %.3f", integration);

 getch();

 return 0;

}

Enter lower limit of integration: 0
Enter upper limit of integration: 1
Enter number of sub intervals: 6

Required value of integration is: 0.784