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rtoy / maxima

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annoying irrelevant asking questions #1657

Open rtoy opened 1 month ago

rtoy commented 1 month ago

Imported from SourceForge on 2024-07-04 22:16:57 Created by zmth on 2013-12-28 05:04:57 Original: https://sourceforge.net/p/maxima/bugs/2669

wxMaxima version: 13.4.0 Maxima version: 5.31.1 Maxima build date: 2013-09-24 09:49:12 Host type: i686-pc-mingw32 Lisp implementation type: GNU Common Lisp (GCL) Lisp implementation version: GCL 2.6.8

:::text
(integrate(exp(-u^2*( (x[1,1]-x[2,1])^2+(x[1,2]-x[2,2])^2+(x[1,3]-x[2,3])^2)),u,-inf,inf) );

now it is obvious (x[1,1]-x[2,1])^2+(x[1,2]-x[2,2])^2+(x[1,3]-x[2,3])^2)) is positive and that is what anyone would assume if they asked for the integral but it comes back and asks questions about positive or negative again and again when it should NOT

NOw if that is not irritating enough I even put in before that:

:::text
(assume(positive,true),assume_pos_pred:true,showtime:true,ratprint:false,load("lrats"))

There is just no excuse for this type of harassment by asking these ignorant lame brain questions !!

rtoy commented 1 month ago

Imported from SourceForge on 2024-07-04 22:16:58 Created by rswarbrick on 2014-02-19 21:42:10 Original: https://sourceforge.net/p/maxima/bugs/2669/#b73d

Some of this seems to be triggered by the subscripts. For example:

:::text
(%i19) integrate(exp(-u^2*((x11-x21)^2+(x12-x22)^2+(x13-x23)^2)), u, -inf, inf);
      2                  2                  2                  2      2      2
Is x23  - 2 x13 x23 + x22  - 2 x12 x22 + x21  - 2 x11 x21 + x13  + x12  + x11
                                                    positive, negative or zero?

pos;
          inf
         /           2             2              2              2
         [        - u  ((x13 - x23)  + (x12 - x22)  + (x11 - x21) )
(%o19)   I      %e                                                  du
         ]
         /
          - inf

With subscripts, you get a confusing looking question with sine, cosine, atan2 and abs! (Presumably the result of realpart or imagpart at some point)

However, it's a little unfortunate that we get asked for a sign at all. I guess that the exponent gets expanded at some point before the sign gets asked. Since the resulting noun form isn't expanded, we presumably gave up on that line of questioning...

Also,

:::text
(%i22) integrate(exp(-u^2 * a), u, -inf, inf);
Is a positive, negative or zero?

pos;
                                   sqrt(%pi)
(%o22)                             ---------
                                    sqrt(a)

which is good. I wonder why the example above gives a noun form instead.

rtoy commented 1 month ago

Imported from SourceForge on 2024-07-04 22:17:02 Created by robert_dodier on 2023-05-04 22:12:08 Original: https://sourceforge.net/p/maxima/bugs/2669/#6d9a

rtoy commented 1 month ago

Imported from SourceForge on 2024-07-04 22:17:05 Created by robert_dodier on 2023-05-04 22:12:08 Original: https://sourceforge.net/p/maxima/bugs/2669/#5702

asksign could be stronger, but I don't see an error in the result reported by OP, and I don't see a difference between using subscripts or not (which would be a bug too). Closing this report as not a bug.