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

atan, atanf, atanl - arc tangent function

#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








These functions calculate the principal value of the arc tangent
    of x; that is the value whose tangent is x.








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.








No errors occur.








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



  

    Interface
    Attribute
    Value
  

  

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










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


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








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








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    the latest version of this page, can be found at
    https://www.kernel.org/doc/man-pages/.







  

    2017-09-15