[Octave-bug-tracker] [bug #62332] [MinGW] acos(z), asin(z) and atan(z) , ( z = x + yi ) return wrong result for imaginary part lower than 1e-12

[Markus Mützel]

Update of bug #62332 (project octave):

                  Status:                    None => In Progress            
                 Release:                   7.1.0 => dev                    

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Follow-up Comment #7:

Octave uses the math functions from the standard libraries.
It looks like the complex inverse trigonometric and hyperbolic functions of
mingw-w64 have accuracy issues for some regimes.
`cacos` and `casin` both depend on the implementation of `casinh`.
I pushed a patch to MXE Octave that should improve the accuracy of these
function if the absolute value of the imaginary part of the input to `casinh`
is smaller than 1 and the absolute value of the real part is small:
https://hg.octave.org/mxe-octave/rev/6f3c099c0d38

That should hopefully cover the case from comment #0.

I didn't have a look at the implementation of `catan` (respectively, `catanh`)
yet.




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