#include <math.h>
#include <stdio.h>                   /* for printf */
void tst_acos (void) {
   float x;
   float y;
   for (x = -1.0; x <= 1.0; x += 0.1) {
      y = acos (x);
      printf ("ACOS(%f) = %f\n", x, y);
   }
}

void tst_asin (void) {
  float x;
  float y;
  for (x = -1.0; x <= 1.0; x += 0.1) {
    y = asin (x);
    printf ("ASIN(%f) = %f\n", x, y);
  }
}

void tst_atan (void) {
  float x;
  float y;
  for (x = -10.0; x <= 10.0; x += 0.1) {
    y = atan (x);
    printf ("ATAN(%f) = %f\n", x, y);
  }
}

void tst_atan2 () {
  float x;
  float y;
  float z;
  x = -1.0;
  for (y = -10.0; y < 10.0; y += 0.1) {
    z = atan2 (y,x);
    printf ("ATAN2(%f/%f) = %f\n", y, x, z);
  }
    /* z approaches -pi as y goes from -10 to 0 */
    /* z approaches +pi as y goes from +10 to 0 */
}