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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 HUGE_VAL, HUGE_VALF,
     and HUGE_VALL, 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.

ERRORS
     These functions will fail if:

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



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Mathematical Library Functions                          atanh(3M)



                     If the integer expression  (math_errhandling
                     &  MATH_ERREXCEPT)  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  (math_errhandling
                     &  MATH_ERREXCEPT)  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(FE_ALL_EXCEPT) before calling these functions.
     On  return,  if  fetestexcept(FE_INVALID  |  FE_DIVBYZERO  |
     FE_OVERFLOW  |  FE_UNDERFLOW)  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.

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


















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Mathematical Library Functions                          atanh(3M)



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|
    | Standard                    | See standards(5).           |
    |_____________________________|_____________________________|


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                    3