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33 votes

Is it always possible to calculate the limit of an elementary function?

EDITED. I use the definition of "elementary function" of Liouville and Ritt (also repeated in Wikipedia). See Ritt's papers in TAMS 25 (1923) 211-222, and TAMS 27 (1925) 68-90. This definition include …
Alexandre Eremenko's user avatar
30 votes

When can an invertible function be inverted in closed form?

I recommend the following paper: MR1501299 Ritt, J. F. Elementary functions and their inverses. Trans. Amer. Math. Soc. 27 (1925), no. 1, 68–90. (freely available on the web). It indeed gives a short …
Alexandre Eremenko's user avatar
6 votes

Decidability of differential equations

If $f$ is a polynomial, then $C^1$ solution is the same as analytic solution. For analytic solutions, very similar questions are considered in the paper MR1011182 Denef, J., Lipshitz, L. Decision pro …
Alexandre Eremenko's user avatar
1 vote

Books/Lecture notes which contrast Risch algorithm with basic standard procedure of finding ...

J. H. Davenport, On the integration of algebraic functions. Lecture Notes in Computer Science, 102. Springer-Verlag, Berlin-New York, 1981. J. H. Davenport, Integration in closed form. Computers in ma …
Alexandre Eremenko's user avatar
1 vote

Is there a bound on the number of connected components of a zero set of an integrable function?

In your example, you can eliminate $\alpha$ by one more differentiation, and obtain that $f=\cos\alpha x$ satisfies $$f'''f-f''f'=0,$$ so the number of components of the zero set cannot be estimated i …
Alexandre Eremenko's user avatar