## Dec 8 2000:

A presentation based on
"Triangles in Euclidean Arrangements,"
by S. Felsner and K. Kriegel,
*Discrete Computational Geometry* **22** (1999), pp. 429-438.

Speaker: Javid Hüseynov, ICS, UC Irvine

The number of triangles in arrangements of lines and pseudolines
has been the object of some research. While most of the results concern
arrangements in the projective plane, this paper presents the results on
the number of triangles in Euclidean arrangements of pseudolines. It
presents another proof by the authors that a simple arrangement of n
pseudolines contains at least n-2 triangles. The best possible bound of
2n/3 triangles in non-simple arrangements of n pseudolines is also
presented in this paper.