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asinh

Section: C Library Functions (3)
Updated: 2026-02-08
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NAME

asinh, asinhf, asinhl - inverse hyperbolic sine function

LIBRARY

Math library (libm,~-lm)

SYNOPSIS

#include <math.h>
double asinh(double x);
float asinhf(float x);
long double asinhl(long double x);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)): asinh():

    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || _XOPEN_SOURCE >= 500
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

asinhf(), asinhl():

    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

These functions calculate the inverse hyperbolic sine of x; that is the value whose hyperbolic sine is x.

RETURN VALUE

On success, these functions return the inverse hyperbolic sine of x. If x is a NaN, a NaN is returned. If x is +0 (-0), +0 (-0) is returned. If x is positive infinity (negative infinity), positive infinity (negative infinity) is returned.

ERRORS

No errors occur.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
asinh(), asinhf(), asinhl()	Thread safety	MT-Safe

STANDARDS

C11, POSIX.1-2008.

HISTORY

C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD.