On 2016-01-21, kcrisman <[email protected]> wrote:

>> Using SageMathCloud I was surprised to find this bug:
>>
>> integral(sqrt(cos(x)-cos(x)^3), x, 0, pi/2)
>> -2/3
>>
>> The correct result is 2/3 (luckily I noticed that something was wrong 
>> because the result must be positive!)

> Usually such things are due to abs_integrate (see e.g. 
> http://trac.sagemath.org/ticket/12731 and 
> http://trac.sagemath.org/wiki/symbolics), but interestingly, abs_integrate 
> comes to the *rescue* when domain:real.  The problem here is due to 
> domain:complex (which is our default).

After looking at this, I think it's a limit bug. domain:complex comes
into play because it causes integrate to return a different form of the
antiderivative, for which the computed limit at 0 is incorrect (although
the behavior of limit seems to be the same for domain:real and
domain:complex).

Reported as: https://sourceforge.net/p/maxima/bugs/3126/

best

Robert Dodier

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