Math & Trig

ACOTH Formula

ACOTH returns the inverse hyperbolic cotangent of a number. The input must have an absolute value greater than 1 (|x| > 1). It's defined as 0.5 × LN((x+1)/(x-1)). ACOTH appears in certain statistical transformations and in solutions to boundary value problems in physics and engineering.

Syntax

ACOTH(number)
ParameterDescription
number Parameter of the ACOTH function.
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Examples

ACOTH of 2

Formula
=ACOTH(2)
Returns ~0.5493. This is 0.5 × LN(3/1) = 0.5 × LN(3) ≈ 0.5493.

ACOTH of 5

Formula
=ACOTH(5)
Returns ~0.2027. As the input grows larger, ACOTH approaches 0.

Verify inverse

Formula
=COTH(ACOTH(3))
Returns 3. Confirms that ACOTH is the inverse function of COTH.

Common Errors

#NUM!

The argument must satisfy |x| > 1. =ACOTH(0.5), =ACOTH(1), and =ACOTH(-1) all return #NUM! because the function is undefined there.

#VALUE!

Non-numeric input returns #VALUE!.

Tips

Domain restriction

ACOTH only accepts x > 1 or x < -1. The interval [-1, 1] is not in the domain. This is the opposite of ATANH, which requires |x| < 1.

Logarithmic formula

ACOTH(x) = 0.5 × LN((x+1)/(x-1)). If your spreadsheet doesn't have ACOTH, you can compute it from LN.

Related to ATANH

ACOTH(x) = ATANH(1/x). They are closely related — ACOTH operates outside [-1,1] while ATANH operates inside.

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