That's correct. If integrate() returns an unevaluated Integral, it
means the algorithm couldn't compute an integral. The fu() function is
able to simplify this expression (it equals 2*sin(x)), so
integrate(fu(fx), x) works.

Aaron Meurer

On Sat, Oct 11, 2014 at 6:06 AM, Francesco Bonazzi
<[email protected]> wrote:
> I guess the algorithm is unable to determine the integral function.
>
> On Saturday, October 11, 2014 8:45:42 AM UTC, Dario Beraldi wrote:
>>
>> Hello,
>>
>> I have the function fx for which I want to evaluate the indefinite
>> integral:
>>
>> x= symbols('x')
>> fx= (sin(4*x) - sin(2*x)) / (cos(3*x))
>> i= integrate(fx)
>> print i
>> ## Integral((-sin(2*x) + sin(4*x))/cos(3*x), x)
>>
>> Now, how can I evaluate i to obtain the "expected" -2*cos(x) + c as per
>> here
>> http://www.wolframalpha.com/input/?i=integrate%28%28sin%284*x%29+-+sin%282*x%29%29+%2F+%28cos%283*x%29%29%29
>>
>> I tried i.evalf(), i.doit() with no luck.
>>
>> Again, many thanks for help!
>>
>> Dario
>
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