# OpenSolaris 2009.06 - man page for atanh (opensolaris section 3m)

atanh(3M) Mathematical Library Functions atanh(3M)atanh, atanhf, atanhl - inverse hyperbolic tangent functionsNAMEc99 [ flag... ] file...SYNOPSIS[ library... ] #include <math.h> double atanh(double x); float atanhf(float x); long double atanhl(long double x);-lmThese functions compute the inverse hyperbolic tangent of their argument x.DESCRIPTIONUpon 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.RETURN VALUESThese functions will fail if: Domain Error The x argument is finite and not in the range [ERRORS,1], or is +-Inf. 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.-1An 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.USAGESee attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ATTRIBUTESfeclearexcept(3M), fetestexcept(3M), math.h(3HEAD), matherr(3M), tanh(3M), attributes(5), standards(5)SEE ALSOSunOS 5.1112 Jul 2006 atanh(3M)