# User talk:Christian1985

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Welcome to Wikidata, Christian1985!

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If you have any questions, please ask me on my talk page. If you want to try out editing, you can use the sandbox to try. Once again, welcome, and I hope you quickly feel comfortable here, and become an active editor for Wikidata.

Best regards! --Leyo 12:14, 22 February 2013 (UTC)

## Babel

Babel lets you view and edit more than one language on Wikidata. Just add e.g. {{#babel:de-N|en-3|es-1|fr-2|nl-3|it-4|da-0}} to your user page. With the same language codes you can add links to your userpage on Wikipedia e.g. de:User:User123. --Tobias1984 (talk) 15:59, 25 August 2013 (UTC)

Thanx for this tip.--Christian1985 (talk) 16:05, 25 August 2013 (UTC)
Gern geschehen. --Tobias1984 (talk) 16:07, 25 August 2013 (UTC)

## de:Glatte Funktion

Hi! Is it true that in German, unlike English and Russian, "smooth function" is always infinitely differentiable? Wikisaurus (talk) 17:46, 26 April 2020 (UTC)

Hello, yes in German a "glatte Funktion" is a function of class ${\displaystyle C^{\infty }}$ . Ich think in English its the same. I looked into the books
• John M. Lee: Introduction to Smooth Manifolds (= Graduate Texts in Mathematics 218). Springer-Verlag, New York NY u. a. 2003, ISBN 0-387-95448-1.
• Lawrence C. Evans: Partial Differential Equations. Reprinted with corrections. American Mathematical Society, Providence RI 2008, ISBN 978-0-8218-0772-9 (Graduate studies in mathematics 19).
• R. Abraham, Jerrold E. Marsden, T. Ratiu: Manifolds, tensor analysis, and applications (= Applied mathematical sciences 75). 2. Auflage. Springer, New York NY u. a. 1988, ISBN 0-387-96790-7.

And they all said, that da smooth function/map is of class ${\displaystyle C^{\infty }}$ . I think the English Wikipedia article [[en:smaoothness}} is not optimal here in the list but better than no article.--Christian1985 (talk) 18:15, 26 April 2020 (UTC)

@user:Wikisaurus What the article of the encyclopedia of mathematics as a smooth function describes is again something different than what I mean by a smooth function and something different than MathWorld means. Therefore, I suggest to delete the item Q92083140 because there are no interwiki links and the literature source of the term is very few. Since there are no linked articles, there are no articles with literature. --Christian1985 (talk) 18:35, 26 April 2020 (UTC)
Well, I found a number of cases like Handbook of Mathematics and A First Course in Analysis, but it indeed looks rather marginal. So ok, I will redirect smooth function (Q92083140) to smooth function (Q868473). Should one label smooth function (Q868473) simply "smooth function" or, to avoid confusion, "infinitely differentiable function"? Wikisaurus (talk) 18:40, 26 April 2020 (UTC)
I would use "smooth function"/"glatte Funktion" because its much more common to read this words in literature than "infinitely differentiable function"/"beliebig oft differentierbare Funktion". Best regards --Christian1985 (talk) 18:49, 26 April 2020 (UTC)