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NAME
       tanh, tanhf, tanhl - hyperbolic tangent functions


SYNOPSIS
       #include <math.h>

       double tanh(double x);
       float tanhf(float x);
       long double tanhl(long double x);


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

       An  application  wishing  to  check for error situations should set errno to zero and call
       feclearexcept(FE_ALL_EXCEPT) before calling these functions.  On return, if errno is  non-
       zero  or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero,
       an error has occurred.


RETURN VALUE
       Upon successful completion, these functions shall return the hyperbolic tangent of x.

       If x is NaN, a NaN shall be returned.

       If x is ±0, x shall be returned.

       If x is ±Inf, ±1 shall be returned.

       If x is subnormal, a range error may occur and x should be returned.


ERRORS
       These functions may fail if:

       Range Error
              The value of x is subnormal.

       If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be
       set  to  [ERANGE].  If  the integer expression (math_errhandling & MATH_ERREXCEPT) is non-
       zero, then the underflow floating-point exception shall be raised.

       The following sections are informative.


EXAMPLES
       None.


APPLICATION USAGE
       On  error,  the  expressions  (math_errhandling  &  MATH_ERRNO)  and  (math_errhandling  &
       MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.


RATIONALE
       None.


FUTURE DIRECTIONS
       None.


SEE ALSO
       atanh() , feclearexcept() , fetestexcept() , isnan() , tan() , the Base Definitions volume
       of IEEE Std 1003.1-2001, Section 4.18, Treatment  of  Error  Conditions  for  Mathematical
       Functions, <math.h>


COPYRIGHT
       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2003 Edition, Standard for Information Technology  --  Portable  Operating  System
       Interface  (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
       the Institute of Electrical and Electronics Engineers, Inc and  The  Open  Group.  In  the
       event  of  any  discrepancy  between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .