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atanh-Hyperbolic Arc Tangent of Angle

Interface 

F_TYPE atanh (F_TYPE x)

Description

atanh() returns the hyperbolic arc tangent of x for x in the interval (-1,1). atanh() is the inverse function of tanh(), where atanh(tanh (x)) = x.

atanh(x) is computed as (1/2 ln((1+x)/(1-x))

Exceptions

Exceptional Argument       Routine Behavior

|x| > or = 1               Invalid argument