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 atan2 3M "12 Jul 2006" "SunOS 5.11" "Mathematical Library Functions"
 NAME
atan2, atan2f, atan2l - arc tangent function

 SYNOPSIS


c99 [ 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 [ -\c
\c
,\c
\c
 ] radians.


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


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


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


If y is > 0 and x is \(+-0, \c
\c
/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, \(+-\c
\c
 is returned.


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


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


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


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


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


If y is \(+-Inf and x is +Inf, \(+-\c
\c
/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 TYPEATTRIBUTE VALUE
Interface StabilityStandard
MT-LevelMT-Safe



 SEE ALSO

atan(3M), isnan(3M), math.h(3HEAD)tan(3M),
attributes(5), standards(5)