In another word, is there any indefinite integral that couldn't find another representation
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2Yes, there are lots. – mjqxxxx May 02 '14 at 20:39
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@mjqxxxx - What is an example? – Victor May 02 '14 at 20:40
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1This is one of them: $$ \int_0^{\Large\frac\pi4} \frac {\sin x} {x \cos^2 x} \mathrm d x. $$At least, how to solve it analytically is unknown yet. Wanna give a try? :) – Tunk-Fey May 02 '14 at 20:45
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One source of examples would be "cheating" by encoding unsolved problems as integral equalities. Sometimes this might be even useful/natural. – Marcin Łoś May 02 '14 at 20:45
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There are general algorithms that give the indefinite integral in terms of given primitives, or show it can't be done. This is more the realm of symbolic computation. – vonbrand May 02 '14 at 20:45
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Something else you could do is look at unanswered questions on SE : http://math.stackexchange.com/questions/tagged/indefinite-integrals?sort=unanswered&pageSize=50 – user88595 May 02 '14 at 20:56
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See http://math.stackexchange.com/questions/155/how-can-you-prove-that-a-function-has-no-closed-form-integral – Martin Sleziak May 02 '14 at 22:23
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here is an example:
http://www.wolframalpha.com/input/?i=int%20%28%28x%2b1%29e%5Ex%29/%28x%281%2bxe%5Ex%29%29dx
$$\int \frac{(x+1)e^x}{x(1+xe^x)} dx$$
There should be a lot of these I think

Martin Sleziak
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Victor
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