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A Generalization of Cox's Chain of Theorems

Published online by Cambridge University Press:  20 November 2018

M. W. Al-Dhahir*
Affiliation:
University of Baghdad and University of Toronto
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In [5, p. 105] attention has been called to a set of propositions, due to H. Cox [3, p. 67], which are related to another set, due to Clifford [2, p. 145; 4, p. 447], concerning points and circles in the plane or on the sphere. One may state Cox's chain of theorems as follows:

In a projective 3-space, S3, let (1), (2), (3), (4) be four points lying in a plane α such that no three of them are collinear. Every two determine a line; let one plane such as [12], pass through each line. There are six such planes. The planes [12], [23], [13] determine a point (123); there are four such points. The first theorem of the chain states that they all lie in one plane [1234], It is not difficult to see that this is, in fact, a rewording of Möbius's theorem on mutually inscribed pairs of tetrahedra [4, p. 444].

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 1961

References

1. Al-Dhahir, M. W., A simplified proof of the Pappus–Leisenring theorem, Michigan Math. J. 4 (1957), 225-226.Google Scholar
2. Brown, Li. M., A configuration of points and spheres in four-dimensional space, Proc. Roy. Soc. Edinburgh Sect. A 34 (1954), 145-149.Google Scholar
3. Cox, H., Applications of Grassmann's Ausdehnungslehre to properties of circles, Quart. J. Math. Oxford 25(1891), 1-71.Google Scholar
4. Coxeter, H. S. M., Self-dual configurations and regular graphs, Bull. Amer. Math. Soc. 56 (1950), 413-455.Google Scholar
5. Richmond, H. W., On a chain of theorems due to Homersham Cox, J. London Math. Soc. 16 (1941), 105-108.Google Scholar