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HP-UX 11i Version 3: February 2007

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atanh(), atanhf(), atanhl(), atanhw(), atanhq() — arc hyperbolic tangent functions


#include <math.h>

double atanh(double x);

HP Integrity Server Only

float atanhf(float x);

long double atanhl(long double x);

extended atanhw(extended x);

quad atanhq(quad x);


atanh() returns the arc hyperbolic tangent of x.

Integrity Server Only

atanhf() is a float version of atanh(); it takes a float argument and returns a float result.

atanhl() is a long double version of atanh(); it takes a long double argument and returns a long double result.

atanhw() is an extended version of atanh(); it takes an extended argument and returns an extended result.

atanhq() is equivalent to atanhl() on HP-UX systems.


To use (for Integrity servers) atanhf(), atanhl(), atanhw(), or atanhq(), compile either with the default -Ae option or with the -Aa and -D_HPUX_SOURCE options.

To use (for Integrity servers) atanhw() or atanhq(), compile also with the -fpwidetypes option.

To use any of these functions, make sure your program includes <math.h>, and link in the math library by specifying -lm on the compiler or linker command line.

For more information, see the HP-UX floating-point guide for HP Integrity servers at the following site: http://www.hp.com/go/fp.


atanh(±0) returns ±0.

atanh(±1) returns ±Inf and raises the divide-by-zero floating-point exception.

If |x| > 1.0, atanh() returns NaN and raises the invalid exception.

If x is NaN, atanh() returns NaN.

When it raises no other exception, whether atanh() raises the inexact exception is unspecified.


If |x| > 1.0, atanh() sets errno to [EDOM].

Integrity Server Only

HP-UX libm functions on Integrity server do not set errno by default. For errno setting, compile with the +Olibmerrno option.


atanh(), atanhf(), atanhl() : ISO/IEC C99 (including Annex F, ``IEC 60559 floating-point arithmetic'')

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