#2669 annoying irrelevant asking questions

None
open
nobody
None
5
2014-02-19
2013-12-28
dan hayes
No

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

(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:

(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 !!

Discussion

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

    (%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,

    (%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.