Parallel programming final exam 3rd question. C function that calculate trapezoidal area.

calculateTrapArea.c

/*
Paralel Programlama Final Soruları
Soru 3)	Argüman olarak n sayısını alan ve geriye trapezoidal alanı döndüren C fonksiyonunu yazınız.
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*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <omp.h>

#define A_POINT 0.0
#define B_POINT 0.8

double f(double x) {
	return 0.2 + 25 * x + -200 * pow(x, 2) + 675 * pow(x, 3) - 900 * pow(x, 4) + 400 * pow(x, 5);
}

/* like the coursebook page:216 */
double calculateArea(int n) {
	double approx, h = 0.0, x_i;

	h = (B_POINT - A_POINT) / n;
	approx = (f(A_POINT) + f(B_POINT)) / 2.0;
	for (int i = 1; i <= n - 1; i++) {
		x_i = A_POINT + i * h;
		approx += f(x_i);
	}
	approx = h * approx;

	return approx;
}

/* from the book's examples*/
double Trap(int n) {
	double integral;
	double h = (B_POINT - A_POINT) / n;
	int k;

	integral = (f(A_POINT) + f(B_POINT)) / 2.0;
	for (k = 1; k <= n - 1; k++) {
		integral += f(A_POINT + k*h);
	}
	integral = integral*h;

	return integral;
}

int main(int argc, char* argv[]) {

	printf("%lf\n", calculateArea(8));

	system("PAUSE");
	return 0;
}