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acosh, acoshf, acoshl - inverse hyperbolic cosine functions


c99 [ flag… ] file-lm [ library… ]
#include <math.h>

double acosh(double x);

float acoshf(float x);

long double acoshl(long double x);


These functions compute the inverse hyperbolic cosine of their argument x.


Upon successful completion, these functions return the inverse hyperbolic cosine of their argument.

For finite values of x < 1, a domain error occurs and NaN is returned.

If x is NaN, NaN is returned.

If x is +1, +0 is returned.

If x is +Inf, +Inf is returned.

If x is −Inf, a domain error occurs and NaN is returned.

For exceptional cases, matherr(3M) tabulates the values to be returned by acosh() as specified by SVID3 and XPG3.


These functions will fail if:

Domain Error

The x argument is finite and less than 1.0, or is −Inf.

If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the invalid floating-point exception is raised.

The acosh() function sets errno to EDOM if x is less than 1.0.


An 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 acosh(). On return, if errno is non-zero, an error has occurred. The acoshf() and acoshl() functions do not set errno.


See attributes(7) for descriptions of the following attributes:


math.h(3HEAD), matherr(3M), cosh(3M), feclearexcept(3M), fetestexcept(3M), standards(7), attributes(7)

solaris/acosh.3m.txt · Last modified: 2023/07/19 08:58 by A User Not Logged in