[Octave-bug-tracker] [bug #60055] regarding to bug #15872: atanh branch cut strangeness

[anónimo]

URL:
  <https://savannah.gnu.org/bugs/?60055>

                 Summary: regarding to bug #15872: atanh branch cut
strangeness 
                 Project: GNU Octave
            Submitted by: None
            Submitted on: dom 14 feb 2021 17:50:34 UTC
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Inaccurate Result
                  Status: None
             Assigned to: None
         Originator Name: Francisco
        Originator Email: frp7000@gmail.com
             Open/Closed: Open
                 Release: 6.1.0
         Discussion Lock: Any
        Operating System: Microsoft Windows

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Details:



I think the principal value (ppv) of atanh is
atanh(z)= 0.5*(log(1+z) -log(1-z)). This is the value used in fortran and
Mathematica.

We cannot use
atanh(z) = 0.5*log((1+z)/(1-z)) this won't give the ppv.

Octave reports for instance, atanh (3) = 0.34 + i pi/2
Which is not the ppv.






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