CAS : issue with SQ( (x)^2 )

[primer]

Hello,

In CAS mode I found that SQ((x)^2) gives x instead of ABS(x).

This makes results wrong, for example if you draw this function : x-SQ((x)^2) you will see it's not zero for negatives numbers, but in CAS it result "0" !

Return exact symbolic result is checked in CAS settings.
firmware revision 8151.

[Arno K]

Well, mine returns abs(x9), have you made an assume(x,...), purge(x) then can help.
Arno

[Marcelo Vanti]

Hello Primer,
the issue here is with the cas settings. The USE i option must be disabled . Please, see the Parisse answer about that here:
http://www.hpmuseum.org/forum/thread-4227.html

[primer]

(09-08-2015 02:11 PM)Marcelo Vanti Wrote:  Hello Primer,
the issue here is with the cas settings. The USE i option must be disabled . Please, see the Parisse answer about that here:
http://www.hpmuseum.org/forum/thread-4227.html

Indeed it works now.

Please note that description is "use i to factor polynomial" but in fact, it's more globally "assume variables are complex".

Thank you.
Best Regards.

[parisse]

No, it's different, Use i on the Prime it's what I call complex mode in Xcas, i.e. assume you work in C. Assumptions on variables is another setting called Complex on the Prime and Complex variables in Xcas. I'm not responsible for the Prime denomination...
I think the best settings configuration is to keep the default for both flags, and use assume(variable,complex) or use csolve/cfactor.