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?

         /           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...


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

(%o22)                             ---------

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