Edwin Woollett wrote:
> On Sept. 05, 2008, Raymond Toy wrote:
>
>>> but direct use of integrate adds "ind" to the
>>> correct answer.
>>>
>>> (%i7) integrate(x*exp(-a*x)*cos( w*x), x, 0, inf);
>>> (%o7) ind - (w^2 - a^2)/(w^4 + 2*a^2*w^2 + a^4)
>>>
>>> Is this a bug?
>>>
>>> Yes this is a bug.
>>
>> Ray
>>
>
> Since maxima can find the indefinite integral, this
> must be a limit(...) bug:
Not necessarily. While I have not had a chance to look at the cause of
the bug, the algorithm for definite integration is usually very, very
different from the typical school method of finding the indefinite
integral and plugging in the limits. Usually, maxima tries to convert
the definite integral into some kind of contour integral and evaluates
that via residues using precomputed results or by explicitly computing
the residues.
Ray