#include <math.h>
float atan2 (
floaty, /* denominator for arc tangent */
floatx); /* numerator for arc tangent */
Description
The atan2 function calculates the arc tangent of the
floating-point ratio y / x.
This function uses the signs of both x and
y to determine the quadrant of the return value.
The floating-point value returned by atan2 is a number in the
range -π to
π.
Return Value
The atan2 function returns the arc tangent of y / x.
For y = 0 and x = 0,
atan2 → NaN.
For y = 0 and x > 0,
atan2 → 0.
For y = 0 and x < 0,
atan2 → 2π.
#include <math.h>
#include <stdio.h> /* for printf */
void tst_atan2 (void) {
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 */
}
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