# atan2f(3m) [sunos man page]

```atan2(3M)						  Mathematical Library Functions						 atan2(3M)

NAME
atan2, atan2f, atan2l - arc tangent function

SYNOPSIS
cc [ flag... ] file... -lm [ library... ]
#include <math.h>

double atan2(double y, double x);

float atan2f(float y, float x);

long double atan2l(long double y, long double x);

DESCRIPTION
These  functions  compute the principal value of the arc tangent of y/x, using the signs of both arguments to determine the quadrant of the
return value.

RETURN VALUES
Upon successful completion, these functions return the arc tangent of y/x in the range [ -, ] radians.

If y is +-0 and x is < 0, +- is returned.

If y is +-0 and x is > 0, +-0 is returned.

If y is < 0 and x is +-0, -/2 is returned.

If y is > 0 and x is +-0, /2 is returned.

If x is 0, a pole error does not occur.

If either x or y is NaN, a NaN is returned.

If y is +-0 and x is -0, +- is returned.

If y is +-0 and x is +0, +-0 is returned.

For finite values of +-y > 0, if x is -Inf,  +- is returned.

For finite values of +-y > 0, if x is +Inf,  +-0 is returned.

For finite values of x, if y is +-Inf, +-/2 is returned.

If y is +-Inf and x is -Inf, +-3/4 is returned.

If y is +-Inf and x is +Inf, +-/4 is returned.

If both arguments are 0, a domain error does not occur.

ERRORS
No errors are defined.

ATTRIBUTES
See attributes(5) for descriptions of the following attributes:

+-----------------------------+-----------------------------+
|      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
+-----------------------------+-----------------------------+
|Interface Stability	     |Standard			   |
+-----------------------------+-----------------------------+
|MT-Level		     |MT-Safe			   |
+-----------------------------+-----------------------------+

SunOS 5.10							    1 Sep 2002								 atan2(3M)```

## Check Out this Related Man Page

```ATAN2(3)						     Linux Programmer's Manual							  ATAN2(3)

NAME
atan2, atan2f, atan2l - arc tangent function of two variables

SYNOPSIS
#include <math.h>

double atan2(double y, double x);
float atan2f(float y, float x);
long double atan2l(long double y, long double x);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

atan2f(), atan2l():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION
These  functions calculate the principal value of the arc tangent of y/x, using the signs of the two arguments to determine the quadrant of
the result.

RETURN VALUE
On success, these functions return the principal value of the arc tangent of y/x in radians; the return value is in the range [-pi, pi].

If y is +0 (-0) and x is less than 0, +pi (-pi) is returned.

If y is +0 (-0) and x is greater than 0, +0 (-0) is returned.

If y is less than 0 and x is +0 or -0, -pi/2 is returned.

If y is greater than 0 and x is +0 or -0, pi/2 is returned.

If either x or y is NaN, a NaN is returned.

If y is +0 (-0) and x is -0, +pi (-pi) is returned.

If y is +0 (-0) and x is +0, +0 (-0) is returned.

If y is a finite value greater (less) than 0, and x is negative infinity, +pi (-pi) is returned.

If y is a finite value greater (less) than 0, and x is positive infinity, +0 (-0) is returned.

If y is positive infinity (negative infinity), and x is finite, pi/2 (-pi/2) is returned.

If y is positive infinity (negative infinity) and x is negative infinity, +3*pi/4 (-3*pi/4) is returned.

If y is positive infinity (negative infinity) and x is positive infinity, +pi/4 (-pi/4) is returned.

ERRORS
No errors occur.

ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).

+-----------------------------+---------------+---------+
|Interface		     | Attribute     | Value   |
+-----------------------------+---------------+---------+
|atan2(), atan2f(), atan2l()  | Thread safety | MT-Safe |
+-----------------------------+---------------+---------+
CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.

The variant returning double also conforms to SVr4, 4.3BSD, C89.