.BG
.FN acosh
.FN asinh
.FN atanh
.TL
Inverse Hyperbolic Trigonometric Functions
.CS
acosh(x)
asinh(x)
atanh(x)
.AG x
numeric or complex.  Missing values (`NA's) are
allowed.
.RT
data transformed by the specified inverse hyperbolic trigonometric function,
with attributes preserved.
Numeric arguments must be at least 1 for `acosh' and must be
less than 1 in absolute value for `atanh', otherwise
.Co NA
is returned and a warning is given.
.Tr
See section 5.1.5 for further details on domains and branch cuts in the
case of complex arguments.
.En
.KW math
.WR
