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Re: Numerical issues with sin()/cos()

From: vlad ionescu
Subject: Re: Numerical issues with sin()/cos()
Date: Tue, 27 Mar 2018 15:29:55 +0000

I have just seen a previous question in the mailing lists, "If pi is
so accurate why it's not producing that accurate result". There
probably are more of the same. Just to clarufy (if there's a
misunderstanding), I am not questioning the inherent floating point
errors, but their consistency. In Octave, sin(-x) doesn't seem to be
equal to -sin(x). This is my main point. As you can see, the the order
of the FIR is odd, so it has two midpoints of equal values coming from
sin(x)/x and sin(-x)/(-x), thus, for all intents and purposes,
sin(x)/x, yet they are not equal. That they differ in Octave and
wxMaxima, so be it, to each their own (numerical evaluation), but why
the two are different whithin Octave is my concern.


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