[Maxima] Bug in changevar. Should I submit the bug report?

Raymond Toy toy.raymond at gmail.com
Thu Mar 22 10:58:50 CDT 2012

On Thu, Mar 22, 2012 at 7:30 AM, Robert Marik <marik at mendelu.cz> wrote:

> Dear all,
>
> I think that the following computation is a bug in changevar. Trying
> substitution cos(x)+sin(x)=t  in  integral of
> (cos(x)+sin(x))^6*(-sin(x)+cos(x))
> I get a mixture of function in t and x variable, see the output of (%o2).
>

This is most likely a failure in solve.  I'm pretty sure changevar uses
solve to express x in terms of t, and solve(t=cos(x)+sin(x),x) -> [sin(x) =
t - cos(x)].

> The same is in version 5.24. Substutitution in
> (cos(x)+sin(x))^(1/6)*(-sin(x)+cos(x))  gives t^(1/6), as expected.
>

I don't follow here, but I guess you really meant cos(x)^(1/6)*sin(x), as
your example shows.  This works because solve(t=cos(x),x) works.

>
> I was not able to find related bugreport. Should I open new one?
>

Yes, that would be very nice if you could.  There's really no harm in
opening a new bug.

Ray
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