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Inverse hyperbolic cotangent
The inverse hyperbolic cotangent is written with logarithms as
Area functions can be described with logarithms because all hyperbolic functions are defined by exponential functions.
Explanation
We'll start with the hyperbolic cotangent
Substitution of eθ = k gives
We continue only with the positive solution and substitute k = eθ so that
Now we take the logarithm from both sides
Substitution of θ = arcoth x gives