On Sun, Mar 29, 2009 at 07:13:25AM -0400, R Fateman wrote:
> Semyon Glazyrin wrote:
>> Hello!
>>
>> When I try to integrate one simple expression maxima asks me about
>> sign of one subexpression. But I think in this case integral limits
>> answer the question:
>>
>> (%i2) assume(a>0,b>0);
>> (%o2) [a > 0, b > 0]
>> (%i3) integrate(sqrt(a/x-b),x,0,a/b);
>> Is b x - a positive, negative, or zero?
>>
>> n; %pi a
>> (%o3) ---------
>> 2 sqrt(b)
>>
>> Does maxima do such type of checks?
>>
>
> sometimes. if you leave out all assumptions it behaves differently, so it
> uses them for something.
>
> if you say assume(b*x-a<0) then it does not ask the question, and just
> gives the answer.
>
> Which behavior represents a bug is not entirely clear. Since x is a
> global variable in the "assume"
> and x is a (presumably different) bound variable in the integration, should
> the assumption have
> any effect? On the other hand, shouldn't the integration program figure
> more of this out itself?
I think it's a problem of integrate function - it should do checks using boundary
conditions.
Semyon.
> RJF
>
>> thanks,
>> Semyon.
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>>
>