[Octave-bug-tracker] [bug #45507] acos returns different results on big input values

[Rik]

Update of bug #45507 (project octave):

                  Status:                    None => Need Info              

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Follow-up Comment #1:

This is probably related to the correction to the phase mentioned in the NEWS
file for 4.0.0


 ** The trigonometric functions asin and acos return different phase values
    from previous versions of Octave when the input is outside the principal
    branch ([-1, 1]).  If the real portion of the input is greater than 1
then
    the limit from below is taken.  If the real portion is less than 1 then
the
    limit from above is taken.  This criteria is consistent with several
other
    numerical analysis software packages.


This was done because 3.8.2 did not calculate the same result as Matlab. 
Could you check your calculations in 3.8.2 because I don't believe they yield
the same result as Matlab.  For 3.8.2 on Linux with the two calculations I
get


acos(1e7)
ans =   0.00000 - 16.81124i
acos(1e8)
ans =   0.00000 - 19.11383i


where the sign of the imaginary portion is negative and the opposite of
Matlab.



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