View source for Flachmacher

==German==
{{was fwotd|de|2022|April|3}}

===Etymology===
Either {{suffix|de|flachmachen|-er}} or {{compound|de|flach|Macher|lit=flat maker}}. Named such because these mappings make the manifold geometrically trivial; they ''[[iron]]'', ''[[straighten]]'' or ''[[flatten]]'' it, intuitively speaking.

===Pronunciation===
* {{IPA|de|/ˈflaxˌmaxəʁ/|[ˈflaχˌmaχɐ]}}
* {{audio|de|De-Flachmacher.ogg}}
* {{hyph|de|Flach|ma|cher}}

===Noun===
{{de-noun|m}}

# {{lb|de|differential geometry}} [[coordinate chart]]
#: {{syn|de|Karte}}
#* {{quote-book|de
|url=https://books.google.ch/books?id=hzEiBAAAQBAJ&lpg=PA106&dq=%22Flachmacher%22&pg=PA103#v=onepage&q=%22Flachmacher%22&f=false
|title=Mathematik 2: Geschrieben für Physiker
|author=Klaus Jänich
|publisher=Springer-Verlag
|series=Springer-Lehrbuch
|isbn=9783642161506
|oclc=1087350906
|date=2011-01-15
|page=103
|passage=Einen solchen Diffeomorphismus <math>H : W \rightarrow W'</math> wollen wir, seiner anschaulichen Bedeutung nach, auch einen <b>''Flachmacher''</b><!-- also bold in the source --> für <math>M</math> um <math>p</math> nennen. In einer anderen Sprechweise heißt ein '''Flachmacher''' <math>H : W \rightarrow W'</math> eine ''äußere Karte''<!-- bold in source --> für <math>M</math> um <math>p \in M</math>, im Unterschied nämlich zur zugehörigen ''inneren Karte'' <!-- bold in source --> <math>H | M \cup W</math>: {{...}}
|t=We want to additionally call such a diffeomorphism <math>H : W \rightarrow W'</math>, in accordance with its illustrative meaning, a <b>''flat maker''</b> for <math>M</math> around <math>p</math>. In another mode of speaking, a '''flat maker''' <math>H : W \rightarrow W'</math> is also named an ''outer chart'' for <math>M</math> around <math>p \in M</math>, in contrast namely to the corresponding ''inner chart'' <math>H | M \cup W</math>: {{...}}
}}

====Usage notes====
* More commonly used in introductory university classes and introductory literature because of its highly self-explanatory nature.
<!-- * Might also be slightly humorous. At least it sounds funny and everybody in class had a chuckle when it was introduced. -->

====Declension====
{{de-ndecl|m}}