Thread: Simpson's rule and Trapezoidal rule from fixed array

Hi!
I am trying to write a program that uses Simpson's rule and Trapezoidal rule from a fixed array. But I am having trouble integrating the array into the rules.

Here is the code

Code:

 #include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <math.h>
//Function prototypes
double f_value (double x);

int main (void){

        int k;
        double f[21], xx[21], del_x, x, s_value, t_value;
        del_x=0.05;
        for (k=0, x=0.; k<=20; k++){
                xx[k]=x;
                f[k]=f_value(x);
                x+= del_x;
        }
        printf ("    x         f(x)\n");
        for(k=0; k<21; k++) printf ("%8.2f %15.4e\n", xx[k], f[k]);
        /*trapezoidal rule*/
        t_value=
        /*Simpson's rule*/
        s_value=
        return;
        }

        double f_value (double x)
        {
        double fx;
        fx=sin(x)* exp(-0.5 *x*x);
        return fx;
        }

thank you!