[Octave-bug-tracker] [bug #59685] sinpi, cospi, sind, cosd small errors

[Rik]

URL:
  <https://savannah.gnu.org/bugs/?59685>

                 Summary: sinpi, cospi, sind, cosd small errors
                 Project: GNU Octave
            Submitted by: rik5
            Submitted on: Mon 14 Dec 2020 02:27:32 PM PST
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Inaccurate Result
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
                 Release: dev
         Discussion Lock: Any
        Operating System: Any

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Details:

The functions named in this bug report are in active development on the
development branch.  I wanted to post a bug report that could be used to track
any problems.

For example, the BIST tests were incomplete so recent changes to make the
algorithm more accurate also caused the functions to lose the ability to
process complex inputs.  Oops.  That capability has been restored, but the
function is still not as accurate as its Matlab equivalent.

For example, cos(x) is an even function so cos (x) == cos (-x).  However, this
is not true for certain values in Octave.  For example,


cosd (67) - cosd(-67)
ans = 5.5511e-17


Matlab gets this right with an error or 0.




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