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On Halpern's conjecture for closed plane curves

Author: Tetsuya Ozawa
Journal: Proc. Amer. Math. Soc. 92 (1984), 554-560
MSC: Primary 53A04; Secondary 52A10
MathSciNet review: 760945
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Abstract: Let $ c$ be a smooth closed plane curve given in general position. A bitangent of $ c$ is, by definition, a line which is tangent to $ c$ at two different points. Let $ B(c)$ and $ D(c)$ denote the numbers of all bitangents and all double points of $ c$, respectively. We prove here that if $ c$ has no inflection points, $ B(c) \leqslant D(c)(2D(c) - 1)$. This is the affirmative answer to Halpern's conjecture.

References [Enhancements On Off] (What's this?)

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Keywords: Closed plane curve, bitangent, double point, inflection point, tangential degree
Article copyright: © Copyright 1984 American Mathematical Society

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