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This is a model representing a generalized cone. The cones are special cases of ruled surfaces. A ruled surface is a surface that can be swept out by a moving line in space. It has a parametrization of the form:
x(u,v) = b(u) + v δ(u),where b is called the director line (or directrix) and δ is the director curve.
x(u,v) = p + v δ(u),where p is a fixed point which can be regarded as the vertex of the cone. The model represents a cone of genus 1. This means that the intersection of this model with a plane gives a smooth curve.
Title model and translation
Kegel dritter Ordnung vom Geschlechte Eins.
A cone of order three of genus one.
Text on Sticker and translation
Prof. Dr. H. Wiener
Darmstadt in 1899
Martin Schilling in Leipzig
Mark 16 or 20
Schilling, M., Catalog mathematischer Modelle für den höheren mathematischen Unterricht, Leipzig: Verlag von Martin Schilling, 1911