Bug or my mistake?

Bugs

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XcasEngGuy
Messages : 145
Inscription : mer. janv. 13, 2010 3:20 pm

Bug or my mistake?

Message par XcasEngGuy » dim. nov. 20, 2022 11:03 pm

I am trying to work with differential equations and found this:
Capture_20221120-175818.jpg
Capture_20221120-175818.jpg (33.12 Kio) Consulté 1773 fois
It appears the integrate function can only integrate dy/dt back to y but not d2 y/dy2 back to dy/dt.

Matt

belanger
Messages : 59
Inscription : jeu. juil. 27, 2017 3:26 pm

Re: Bug or my mistake?

Message par belanger » lun. nov. 21, 2022 3:45 am

Also, it doesn't integrate dy/dt back to y if it is entered as
diff(y(t),t).
If you enter
eq1 := diff(y(t),t,1)
then again
int(eq1,t)
returns undef.
Oddly, perhaps,
diff(y(t),t,1)
returns
diff(y(t),t,1)
I expected
diff(y(t),t)

Jay

XcasEngGuy
Messages : 145
Inscription : mer. janv. 13, 2010 3:20 pm

Re: Bug or my mistake?

Message par XcasEngGuy » lun. nov. 21, 2022 11:54 pm

It appears that any diff command with 3 arguments won't integrate back. int(diff(y(t),t),t) seems to work for me.

cygwin xcas
xcas 1.9.0-29 (c) 2000-18
Win 10 22H2
Capture_20221121-184922.jpg
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parisse
Messages : 5731
Inscription : mar. déc. 20, 2005 4:02 pm
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Re: Bug or my mistake?

Message par parisse » jeu. nov. 24, 2022 1:09 pm

Well, Xcas is not really implemented for solving these kinds of integrals, it expects defined symbolic argument. I'm able to fix these simple examples, but integration by part for example will not work.

XcasEngGuy
Messages : 145
Inscription : mer. janv. 13, 2010 3:20 pm

Re: Bug or my mistake?

Message par XcasEngGuy » ven. nov. 25, 2022 6:41 pm

Fixing these simple examples would help me a lot.

Matt

XcasEngGuy
Messages : 145
Inscription : mer. janv. 13, 2010 3:20 pm

Re: Bug or my mistake?

Message par XcasEngGuy » ven. janv. 06, 2023 5:21 pm

Thank you, works great now.

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