On 12/11/06, Daniel Lakeland <dlakelan at street-artists.org> wrote:
> integrate(abs(sin(x)/x),x,0,inf) asks the seemingly stupid question:
> Is ind positive, negative, or zero?
>
> the user has absolutely no idea what maxima is asking... I'm going to
> assume that it has something to do with a change of variable deep
> within the integrator... but it's completely opaque to me.
This is definitely a bug, and should be reported. Integrate is
calling limit, and the bug is actually in the limit routine:
limit( abs(sin(x))/x , x , inf) => asks sign of ind
IND is supposed to be used by Limit as a return value meaning that the
limit set is bounded, e.g. limit(sin(x),x,inf) => ind, but obviously
here it's gotten its wires crossed.
I suggest you write up the limit bug with a note that definite
integration encounters it.
By the way, I wouldn't hold out much hope for calculating definite
integrals involving any non-trivial absolute values. Maxima can't
even handle trivial cases like integrate(abs(sin(x)),x,0,%pi) -- where
it should be able to simplify abs(sin(x)) to sin(x) given the range of
x.
-s