problem getting all root solutions in maxima

Thanks for the answers!
I tried changing the interval according to each root(by looking in the
graph) and it worked except at one, which gives me some big expression.

What i have is:
f(x):=%e^(-abs(x-2))*cos((3/2)*x+(1/5)); (the function)
df(x):=''(diff(f(x),x)); (the derivative - the one I'm calculating the
roots)

the interval is:
a:-4.322123538119724;
b:4.055456871453057;
(this was calculated before but no need to add that in this, so i just wrote
the results)

so i did a graph and saw where the roots are, and in the find_root()
function i changed the interval. But in the interval: [1,3] i get this:

root4:find_root(df(x), x, 1, 3);
*****find_root(-(3*%e^(-abs(x-2))*sin((3*x)/2+1/5))/2-((x-2)*%e^(-abs(x-2))*cos((3*x)/2+1/5))/abs(x-2),x,1.0,3.0)*****


On Tue, Jan 12, 2010 at 4:38 PM, Barton Willis <willisb at unk.edu> wrote:

> Yes, this is the right list to send such questions.
>
> The function find_root is a numerical method that finds at most one
> root in a given interval.  If you know something about where the roots
> are located (say graphically), you could apply find_root multiple
> times to disjoint intervals to find the remaining roots.
>
> You could also try to use the function solve to determine the roots,
> but unless you could solve the equation by hand, it's not all that
> likely that solve will be able to find the roots either.
>
> Barton
>
> maxima-bounces at math.utexas.edu wrote on 01/11/2010 06:34:41 PM:
>
> > [image removed]
> >
> > [Maxima] problem getting all root solutions in maxima
> >
> > Pedro Ferreira
> >
> > to:
> >
> > maxima
> >
> > 01/12/2010 09:16 AM
> >
> > Sent by:
> >
> > maxima-bounces at math.utexas.edu
> >
> > Hello, don't know if I'm sending to the right email, anyway here's
> > my problem. I'm trying to get all the zeros of a function in a
> > certain interval. What I did was:
> >  find_root(df(x), x, a, b);
> > df(x) is my function, a and b the intervals.
> > What i get is the x of one of the zeros, but there's more than 1
> > zero on that interval, but I'm not seeing how do i get all the x's
> > corresponding to all the zeros.
> > I think there's some sort of trick where you put a variable in the
> > command, and by changing the value(0,1,2,3...) you get all the
> > zeros, but I'm not seeing how to do here.
> >
> > thanks for your time_______________________________________________
> > Maxima mailing list
> > Maxima at math.utexas.edu
> > http://www.math.utexas.edu/mailman/listinfo/maxima
>
>