ACOSH(3) | Library Functions Manual | ACOSH(3)

# NAME

`acosh`, `acoshf`, `acoshl` — inverse hyperbolic cosine functions

# SYNOPSIS

Math Library (libm, -lm)
`#include <math.h>`

double
`acosh`(double x);

float
`acoshf`(float x);

long double
`acoshl`(long double x);

# DESCRIPTION

The `acosh`() function computes the inverse hyperbolic cosine of the real argument x. The `acoshf`() function is a single precision version of `acosh`(). The `acoshl`() function is an extended precision version of `acosh`().

# RETURN VALUES

If x is less than one, `acosh`(x), `acoshf`(x) and `acoshl`(x) return NaN and set the global variable errno to `EDOM`.

# SEE ALSO

asinh(3), atanh(3), exp(3)

# HISTORY

The `acosh`() function appeared in 4.3BSD.

June 7, 2025 | Debian