Karel Petr

{{Short description|Czech mathematician}} {{Use list-defined references|date=June 2024}} thumb|160px|Petr in 1928 '''Karel Petr''' ({{IPA|cs|ˈkarɛl ˈpɛtr̩|-}}; 14 June 1868 – 14 February 1950) was a Czech mathematician.

==Biography== Petr was born on 14 June 1868 in Zbyslav Bohemia, Austria-Hungary (today part of Vrdy, Czech Republic).<ref name=MasarykU>{{cite web | title=Karel Petr | website=The Department of Mathematics and Statistics of the Faculty of Science, Masaryk University | url=http://web.math.muni.cz/biografie/karel_petr.html | language=cs}}</ref> He is known for the Petr–Douglas–Neumann theorem in plane geometry, which he proved in 1905 (in Czech)<ref>{{cite journal | last=Petr | first=Karel | title=O jedné vete pro mnohoúhelníky rovinné | trans-title = On a theorem for the plane polygons | journal=Casopis pro pestování matematiky a fysiky | volume=34 | issue=2 | date=1905 | issn=1802-114X | doi=10.21136/CPMF.1905.120936 | pages=166–172 | language=cs | url = https://dml.cz/bitstream/handle/10338.dmlcz/120936/CasPestMatFys_034-1905-2_8.pdf}}</ref> and in 1908 (in German).<ref>{{cite journal|first=Karel| last= Petr|title=Ein Satz über Vielecke|journal=Arch. Math. Phys.|year=1908|volume=13|pages=29–31}}</ref><ref name=Gray>{{cite journal|last=Stephen B. Gray|title=Generalizing the Petr–Douglas–Neumann Theorem on ''n''-gons|journal=American Mathematical Monthly|volume=110|issue=3|pages=210–227|url=http://www.experimentalmath.info/workshop2004/gray-article.pdf|doi=10.2307/3647935|jstor=3647935|year=2003|citeseerx=10.1.1.605.2676}}</ref> It was independently rediscovered by Jesse Douglas in 1940<ref>{{cite journal|last=Douglas|first=Jesse|title=On linear polygon transformations|journal=Bulletin of the American Mathematical Society|year=1940|volume=46|issue=6|pages=551–561|url=https://www.ams.org/journals/bull/1940-46-06/S0002-9904-1940-07259-3/S0002-9904-1940-07259-3.pdf|doi=10.1090/s0002-9904-1940-07259-3|doi-access=free}}</ref> and by Bernhard Neumann in 1941.<ref name=Gray/><ref>{{cite journal|last=B H Neumann|title=Some remarks on polygons|journal=Journal of the London Mathematical Society |year=1941|volume=s1-16|issue=4 |pages=230–245|doi=10.1112/jlms/s1-16.4.230}}</ref>

Eduard Čech was a doctoral student of Petr at Charles University in Prague. Petr's doctoral students also included Bohumil Bydžovský and Václav Hlavatý.<ref>{{MathGenealogy|id=129344}}</ref>

Petr died on 14 February 1950 in Prague.<ref name=MasarykU/>

== References == {{reflist}}

==External links== * [https://dml.cz/browse-author-items?id=8373 Author: Petr, Karel] on Czech Digital Mathematics Library

{{DEFAULTSORT:Petr, Karel}} Category:1868 births Category:1950 deaths Category:People from Kutná Hora District Category:Czech mathematicians Category:Czechoslovak mathematicians Category:Mathematicians from Bohemia Category:Charles University alumni Category:Academic staff of Charles University Category:Mathematicians from Austria-Hungary Category:Burials at Vinohrady Cemetery