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ATAN(3) Linux Programmer's Manual ATAN(3)

NAME

atan, atanf, atanl - arc tangent function

SYNOPSIS

#include <math.h>
double atan(double x);
float atanf(float x);
long double atanl( long double x);


Link with -lm.




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


atanf(), atanl():


_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 x; 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
  

  

    atan (), atanf (), atanl ()
    Thread safety
    MT-Safe
  








CONFORMING TO


C99, POSIX.1-2001, POSIX.1-2008.


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






SEE ALSO


acos(3), asin(3), atan2(3), carg(3),
    catan(3), cos(3), sin(3), tan(3)






COLOPHON


This page is part of release 5.10 of the Linux man-pages
    project. A description of the project, information about reporting bugs, and
    the latest version of this page, can be found at
    https://www.kernel.org/doc/man-pages/.







  

    2017-09-15