Serial trapezoidal rule Calculate definite integral using trapezoidal rule. * The function f(x) is hardwired.

/* serial.c -- serial trapezoidal rule
*
* Calculate definite integral using trapezoidal rule.
* The function f(x) is hardwired.
* Input: a, b, n.
* Output: estimate of integral from a to b of f(x)
* using n trapezoids.
*
* See Chapter 4, pp. 53 & ff. in PPMPI.
*/

#include

main() {
float integral; /* Store result in integral */
float a, b; /* Left and right endpoints */
int n; /* Number of trapezoids */
float h; /* Trapezoid base width */
float x;
int i;

float f(float x); /* Function we're integrating */

printf("Enter a, b, and n\n");
scanf("%f %f %d", &a, &b, &n);

h = (b-a)/n;
integral = (f(a) + f(b))/2.0;
x = a;
for (i = 1; i <= n-1; i++) {
x = x + h;
integral = integral + f(x);
}
integral = integral*h;

printf("With n = %d trapezoids, our estimate\n",
n);
printf("of the integral from %f to %f = %f\n",
a, b, integral);
} /* main */


float f(float x) {
float return_val;
/* Calculate f(x). Store calculation in return_val. */

return_val = x*x;
return return_val;
} /* f */