Name
atan, atanf, atanl - arc tangent functionLibrary
Math library ( libm ", " -lm )Synopsis
#include <math.h> double atan(double x );Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
float atanf(float x );
long double atanl(long double x );
atanf() atanl()
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
Description
These functions calculate the principal value of the arc tangent ofx ;
that is the value whose tangent is x
. Return Value
On success, these functions return the principal value of the arc tangent of x in radians; the return value is in the range [-pi/2,\ pi/2].If x is a NaN, a NaN is returned.
If x is +0 (-0), +0 (-0) is returned.
If x is positive infinity (negative infinity), +pi/2 (-pi/2) is returned.
Errors
No errors occur.Attributes
For an explanation of the terms used in this section, see attributes(7).Interface | Attribute | Value |
T} | Thread safety | MT-Safe |
Standards
C11, POSIX.1-2008.History
C99, POSIX.1-2001.The variant returning double also conforms to SVr4, 4.3BSD, C89.