**Public Function ATanH( _
ByVal vX As Variant _
) As Variant**

**"Inverse Hyperbolic Tangent" **

Angle whose hyperbolic tangent is X.

Inverse of the TanH function.

**Examples:** ATanH(-10) = "-0.100335351042444|1.5707963267949"
ATanH(-2) = "-0.549306129432895|1.5707963267949"
IsNull(ATanH(-1)) = True
ATanH(-0.5) = -0.549306144334055
ATanH(0) = 0
ATanH(0.5) = 0.549306144334055
IsNull(ATanH(1)) = True
ATanH(2) = "0.549306144334055|1.5707963267949"
ATanH(10) = "0.100335342312472|1.5707963267949"
ATanH("2.3|-4.5") = "0.087545427889694|-1.39503801025295"

**See also:** ATan Function
TanH Function
ASinH Function
ACosH Function
HArctan Function

**vX:** Function returns the principal value of the angle whose hyperbolic tangent (expressed in radians) is vX. Function returns Null if vX is Null or cannot be fixed up to a real or complex number (as defined by the ComplexStringToReals function). Complex numbers are represented within strings as "R|I" where R is the real part and I is the imaginary part.

**Note:** Microsoft named this function HArctan within their Derived Math Function help topic. **Definition:**

Logarithm(- (X + 1) / (X - 1)) / 2

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