Inverse Hyperbolic Trigonometric Functions
DESCRIPTION:
Performs inverse hyperbolic trigonometric transformations on real or complex numbers.
USAGE: 
acosh(x)
asinh(x)
atanh(x)
REQUIRED ARGUMENTS:
x:
numeric or complex. Missing values (NAs) are allowed.
VALUE:
data transformed by the specified inverse hyperbolic trigonometric function, with attributes preserved.
DETAILS:
Numeric arguments must be at least 1 for acosh and must be less than 1 in absolute value for atanh, otherwise is returned and a warning is given.

These functions are part of the Math group of generic functions.

See section 5.1.5 of Becker, Chambers and Wilks for further details on domains and branch cuts in the case of complex arguments.

SEE ALSO:
acos , cosh .
EXAMPLES: 
# be sure you have a graphics window open
plot(acosh(sort(abs(rnorm(500))+1)))
plot(asinh(sort(rnorm(500))))
plot(atanh(seq(-1,1, len = 500)))