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


     atanh, atanhf, atanhl - inverse hyperbolic tangent function


     #include <math.h>
     double atanh(double x);
     float atanhf(float x);
     long double atanhl(long double x);
     Link with -lm.
 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
         _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
             || _XOPEN_SOURCE >= 500
             || /* Since glibc 2.19: */ _DEFAULT_SOURCE
             || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
     atanhf(), atanhl():
         _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
             || /* Since glibc 2.19: */ _DEFAULT_SOURCE
             || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE


     These  functions calculate the inverse hyperbolic tangent of x; that is
     the value whose hyperbolic tangent is x.


     On success, these functions return the inverse hyperbolic tangent of x.
     If x is a NaN, a NaN is returned.
     If x is +0 (-0), +0 (-0) is returned.
     If  x  is  +1  or  -1,  a  pole  error occurs, and the functions return
     HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively,  with  the  mathemati-
     cally correct sign.
     If  the  absolute  value of x is greater than 1, a domain error occurs,
     and a NaN is returned.


     See math_error(7) for information on how to determine whether an  error
     has occurred when calling these functions.
     The following errors can occur:
     Domain error: x less than -1 or greater than +1
            errno  is  set  to  EDOM.   An  invalid floating-point exception
            (FE_INVALID) is raised.
     Pole error: x is +1 or -1
            errno is set to ERANGE (but see BUGS).  A divide-by-zero  float-
            ing-point exception (FE_DIVBYZERO) is raised.


     For   an   explanation   of   the  terms  used  in  this  section,  see
     allbox; lbw28 lb lb  l  l  l.   Interface Attribute Value  T{  atanh(),
     atanhf(), atanhl() T}   Thread safety  MT-Safe


     C99, POSIX.1-2001, POSIX.1-2008.
     The variant returning double also conforms to SVr4, 4.3BSD.


     In  glibc  2.9  and  earlier, when a pole error occurs, errno as set to
     EDOM instead of the POSIX-mandated ERANGE.  Since version  2.10,  glibc
     does the right thing.


     acosh(3), asinh(3), catanh(3), cosh(3), sinh(3), tanh(3)


     This  page  is  part of release 4.16 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
                                2017-09-15                          ATANH(3)
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