@prefix psr: <http://data.loterre.fr/ark:/67375/PSR> .
@prefix skos: <http://www.w3.org/2004/02/skos/core#> .

psr: a skos:ConceptScheme .
psr:-BP0VLKCT-T
  skos:definition """En géométrie différentielle, une famille de courbes planes possède fréquemment une courbe enveloppe. Celle-ci admet deux définitions géométriques traditionnelles, presque équivalentes : 
<br/>- l'enveloppe est une courbe tangente à chacune des courbes de la famille;
<br/>- elle est le lieu des points caractéristiques, points d'intersection de deux courbes infiniment proches.
<br/>De façon plus précise, l'enveloppe possède une définition analytique, c'est l'ensemble des points critiques de l'application de projection associée à la famille de courbes. 
<br/>(Wikipedia, L'Encylopédie Libre, <a href="https://fr.wikipedia.org/wiki/Enveloppe_(g%C3%A9om%C3%A9trie)">https://fr.wikipedia.org/wiki/Enveloppe_(g%C3%A9om%C3%A9trie)</a>)"""@fr, """In geometry, an envelope of a planar family of curves is a curve that is tangent to each member of the family at some point, and these points of tangency together form the whole envelope. Classically, a point on the envelope can be thought of as the intersection of two "infinitesimally adjacent" curves, meaning the limit of intersections of nearby curves. This idea can be generalized to an envelope of surfaces in space, and so on to higher dimensions. To have an envelope, it is necessary that the individual members of the family of curves are differentiable curves as the concept of tangency does not apply otherwise, and there has to be a smooth transition proceeding through the members. But these conditions are not sufficient – a given family may fail to have an envelope. A simple example of this is given by a family of concentric circles of expanding radius. 
<br/>(Wikipedia, The Free Encyclopedia, <a href="https://en.wikipedia.org/wiki/Envelope_(mathematics)">https://en.wikipedia.org/wiki/Envelope_(mathematics)</a>)"""@en ;
  a skos:Concept ;
  skos:inScheme psr: ;
  skos:broader psr:-WFQQ48RG-8 ;
  skos:prefLabel "envelope"@en, "enveloppe"@fr ;
  skos:exactMatch <https://fr.wikipedia.org/wiki/Enveloppe_(g%C3%A9om%C3%A9trie)>, <https://en.wikipedia.org/wiki/Envelope_(mathematics)> .

psr:-WFQQ48RG-8
  skos:prefLabel "plane curve"@en, "courbe plane"@fr ;
  a skos:Concept ;
  skos:narrower psr:-BP0VLKCT-T .