# Re: an old bug on the 85

Yeah, this turns out not to be a bug at all, but has to do with Hermitian
matrices.  The Hermitian is a transpose where each element is also replaced
with its complex conjugate.

geoffh

stephen soltesz wrote:

> > I recall less than a year ago someone reporting a bug on the 85
> > involving complex numbers and (this is what I've forgotten) either the
> > dot() or cross() product.  I played with both using complex numbers and
> > didn't see any problem.. but need to know what it was or what caused it,
> > so as not to mess any calculations up..
> >
> > So, if anyone knows to what I am referring, or if it was a different
> > function, let me know.  I remember it relating to EE majors, for some
> > reason.
> >
> > thankyou.
> > stephen.
> >
>
> As an interesting follow-up to this bug is another manifestation I
> discovered while trying to find an easy workaround.
> I wanted to make two 1x2 matrixes take the first, then transpose the
> second and multiply the two.. 1x2 * 2x1 and get a 1x1 answer.
>
> As it turns out, if you transpose a complex matrix, say [[(a,b),(c,d)]]
> you will get
> [[(a,-b)]
>  [(c,-d)]]
> This occurs for any dimension complex matrix  MxN.
> Based on this, I'd guess that the vector functions are a subset of the
> matrix operations already in ROM.  More specifically the transpose
> function.  When someone calls the dot() function the ti pretends you
> have two 1xN matrixes,  transposes the second and multiplies the two.
> This is consistent with what I've observed, but I may be confusing the
> correlation with simple causality.
>
> I now have two questions as a result of this.  I found four FAQ's on the
> internet.
> 1. maintained by ticalc.org  2. By TI itself  3. by Ray Kremer  4. by
> Stephan Bird.
> was on none of them... Why?
>
> The second question is, does this problem manifest itself in the current
> ti-86 rom.. and if so WHY!!??
>
> Please reguard these questions as merely rhetorical.. The fact that I
> have a buggy calc has gotten me a little pissed.
>
> --
>         "I will take my hands and weave them to a little house,
>          and there you shall keep a dream--"
>                         --Miriamne. "Winterset"

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