Beiträge zur Algebra und Geometrie Contributions to Algebra and Geometry Vol. 49, No. 1, pp. 195203 (2008) 

A projective characterization of cyclicityWladimir G. Boskoff and Bogdan D. SuceavaDepartment of Mathematics and Computer Science, University Ovidius Constanta, Romania, email: boskoff@univovidius.ro, Department of Mathematics, California State University at Fullerton, Fullerton, CA, 928346850, U.S.A., email: bsuceava@fullerton.eduAbstract: In this note we obtain a new cyclicity criterion for four points in the Euclidean plane, by using algebraic and geometric structures induced in $\mathbb{C}^2$ by the two dimensional complex projective space. We show that if four points lie on a circle in the real plane, then the typeone isotropic lines intersect $z_2$axis in four points of real cross ratio. Classification (MSC2000): 51N15; 51M05 Full text of the article:
Electronic version published on: 26 Feb 2008. This page was last modified: 28 Jan 2013.
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