HP 40GS CAS cannot integrate X*SIN(X)

[Andreas Debus]

(10-16-2024 07:04 PM)gavenkoa Wrote:  I've bought HP 40GS for CAS (found few 39GS too for a low price on EBay too) and my physical calculator cannot integrate INTVX(X*SIN(X)), it reports 2 subsequent warnings:

* Warning, integrating in approx mode
* Error: Result not editable in EQW

I downloaded official emulator, https://www.educalc.net/page/2336221/ and it reports same VERSION:

Code:

  Version HP39-E
  Copyright HP,
  1993-2010
  Revision 2.23

and CAS there reports "Linearizing" and then solves integral in complex numbers: -(X-i)/2*exp(-i*X) -(X+i)/2*exp(i*X).

Emu48 on Android with 40GS Erik's skin reporting VERSION as "HP39-A Copyright 1993,2000", reports same integral as SIN(X)-X*COS(X).

I don't understand why I see different results and why physical calculator result is the most unhelpful...

In the first case you activated the APPROX flag in the CAS settings of your physical calculator. In the second case you activated the COMPLEX flag in the CAS settings.
That way I was able to reprocduce your "errors" which are exactly what is supposed to happen. The formula you see in the second case is just x*sin(x) in a more complicated form, because e^(ix) is cos(x)+isin(x) .