Mathematical Library Functions                          atanh(3M)



NAME
     atanh, atanhf, atanhl - inverse hyperbolic tangent functions

SYNOPSIS
     c99 [ flag... ] file... -lm [ library... ]
     #include 

     double atanh(double x);


     float atanhf(float x);


     long double atanhl(long double x);


DESCRIPTION
     These functions compute the inverse  hyperbolic  tangent  of
     their argument x.

RETURN VALUES
     Upon  successful  completion,  these  functions  return  the
     inverse hyperbolic tangent of their argument.


     If x is ]1, a pole error occurs and atanh(),  atanhf(),  and
     atanhl()  return the value of the macro HUGEVAL, HUGEVALF,
     and HUGEVAL, respectively,  with  the  same  sign  as  the
     correct value of the function.


     For finite x > 1, a domain  error  occurs  and  a  NaN  is
     returned.


     If x is NaN, NaN is returned.


     If x is ]0, x is returned.


     If x is ]Inf, a domain error occurs and a NaN is returned.


     For exceptional cases, matherr(3M) tabulates the  values  to
     be returned by atanh() as specified by SVID3 and XPG3.

ERORS
     These functions will fail if:

     Domain Error    The x argument is  finite  and  not  in  the
                     range [-1,1], or is ]Inf.



SunOS 5.11          Last change: 12 Jul 2006                    1






Mathematical Library Functions                          atanh(3M)



                     If the integer expression  (matherrhandling
                     &  MATHEREXCEPT)  is non-zero, the invalid
                     floating-point exception is raised.

                     The atanh() function sets errno to  EDOM  if
                     the absolute value of x is greater than 1.0.


     Pole Error      The x argument is ]1.

                     If the integer expression  (matherrhandling
                     &  MATHEREXCEPT)  is  non-zero,  then  the
                     divide-by-zero floating-point  exception  is
                     raised.

                     The atanh() function sets errno to ERANGE if
                     the absolute value of x is equal to 1.0.


USAGE
     An application wanting to check for exceptions  should  call
     feclearexcept(FEALEXCEPT) before calling these functions.
     On  return,  if  fetestexcept(FEINVALID    FEDIVBYZERO  
     FEOVERFLOW    FEUNDERFLOW)  is non-zero, an exception has
     been raised. An application should either examine the return
     value  or check the floating point exception flags to detect
     exceptions.


     An application can  also  set  errno  to  0  before  calling
     atanh().  On  return,  if  errno  is  non-zero, an error has
     occurred. The atanhf() and atanhl()  functions  do  not  set
     errno.

ATRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     
           ATRIBUTE TYPE               ATRIBUTE VALUE       
    
     Interface Stability          Standard                    
    
     MT-Level                     MT-Safe                     
    


SEE ALSO
     feclearexcept(3M),     fetestexcept(3M),      math.h(3HEAD),
     matherr(3M), tanh(3M), attributes(5), standards(5)



SunOS 5.11          Last change: 12 Jul 2006                    2