On Fri, May 16, 2025 at 01:40:55PM +0200, Grégory Vanuxem wrote:
> Hello Waldek, *
>
> Le jeu. 15 mai 2025 à 22:53, Waldek Hebisch <de...@fricas.org> a écrit :
>
> > On Thu, May 15, 2025 at 07:40:39PM +0200, Grégory Vanuxem wrote:
>
> >
> >
> > If you wander why FriCAS leaves asin(sin(x)) unsimplified, this
> > is due to branches, sin(x) = sin(x + 2*%pi), applaying asin
> > to both sides and using unsound transformation of asin(sin(x))
> > to x would give false equality x = x + 2*%pi. Similarly,
> > pulling %i before square roots leads to nonsense like the last
> > result in the following mail.
> >
>
> The second mail use behind the scene Mathematica (jWSExpression)
>
> I can agree that, in general, branches can interfere but in this case,
> applying the operations used here on -3/2 should return from my point of
> view -3/2. That's just surprising for me. Other CAS returns in fact -3/2
> and that's correct.
Yes, in this case it is what you want. Transformation 'asin(sin(x))'
to 'x' was in NAG Axiom, it was blocked later because it may lead to
wrong results.
> I find it's a pity for FriCAS.
--
Waldek Hebisch
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