acosh function

Synopsis

$acosh(number)

Technical

acosh() calls the C library's acosh() function to return the inverse hyperbolic cosine of number. For finite inputs, number must be at least 1; the result is nonnegative. cosh() performs the corresponding hyperbolic cosine operation.

The normal rules about number arguments apply. The first argument word is converted with atof(), accepting decimal fractions and scientific notation; additional words are ignored. Missing input returns the empty string. Nonnumeric input converts to zero, which is outside this function's domain. A numeric prefix can be accepted even when followed by nonnumeric text.

Returns and restrictions

The calculation uses a C double, and the result is formatted with %.50g. The floating_point_math and floating_point_precision settings do not change this function's calculation or formatting. Returned rounding digits do not imply 50 digits of accuracy.

An argument below 1 causes a library domain error. EPIC returns DOM when the library reports that error through errno; if the platform reports it only through a floating-point exception, the result can instead be a NaN string. The shared wrapper returns RANGE for a reported range error and the empty string for another reported error. It checks errno, not floating-point exception flags, so callers should validate the input rather than assume one particular error string.

This built-in has no optional configure-time gate; it relies on the platform math library.

Examples

The approximate example describes the numeric value; the returned string may contain more digits.

Source

source/functions.c registers acosh and implements function_acosh through the shared math-function and error-return macros. include/functions.h defines argument conversion and formatting. The C/POSIX inverse hyperbolic cosine specification defines the domain and library error reporting.