Edwin Woollett wrote:
> Ray writes (this is good information for a neophyte to know!):
>
> "It uses the internal variable yx and wants to solve the equation yx = exp(sqrt(x)) for x. I guess it needs to know the sign of yx to solve this."
>
> My naive comments:
>
> 1. Minimal help to user: include this message inside of integrate() - user interaction when asking a question about an internal variable yx whose function is normally hidden from the user.
I suppose that's possible, but not very appealing. Maxima shouldn't ask
at all.
>
> 2. More help to user: examine range of integration variable (x), determine if sign of integrand is constant over that integration range, and if so, determine the sign of yx from that information.
I think that's a hard problem in general, although it ought to be easy
for this particular case since the exp(x) is always positive. But
maxima wasn't asking for the sign of x; it wanted the sign of yx.
>
> 3. Even more help: split up the integral into a sum of integrals, for each of which one can determine the sign of yx.
I think that's basically equivalent to finding the roots of the
integrand, which is quite hard.
I don't have a good solution for this. But at least you now know what
yx means. :-)
Ray