Roadmap proposal for 3.10/4.0

Michael Nedzelsky MichaelNedzelsky at yandex.ru
Tue Oct 17 19:55:06 UTC 2006


On Tue, 17 Oct 2006 11:31 pm, Hans-Martin Mosner wrote:
> Damien Cassou schrieb:
> > Ken Dickey a Иcrit :
> >>   -4 sqrt. "2.0i"
> >
> > If I remember correctly what my math teacher taught me, this is
> > incorrect.
> >
> >
> > Rule of square roots:
> > ---------------------
> > a sqrt * b sqrt = (a*b) sqrt
> >
> > Applied to -4:
> > --------------
> > (-4) sqrt * (-4) sqrt = 16 sqrt = 4
> >
> > With your equality:
> > -------------------
> > (-4) sqrt * (-4) sqrt = 2i * 2i = -4
> >
> >
> > We then have the same expression returning two different values. My
> > teacher concluded saying "sqrt is a function only valid for positive
> > numbers"
>
> Your math teacher had a limited horizon (or you remember incorrectly).
> I would rather conclude "the Rule of square roots is only valid for
> positive numbers".
I am sorry, but "the Rule of square roots is only valid for
nonnegative numbers".

Michael Nedzelsky




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