Spherical Conic and the Fourth Parameter

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Yoichi Maeda

Abstract

As the same as planner ellipse in Euclidean plane, spherical ellipse on the unit sphere is determined by two parameters: two foci and a string with certain length. Spherical ellipse is also the intersection of an elliptic cone centered at the origin and the unit sphere. Spherical ellipse has three parameters; focus, major axis, and minor axis. In this paper, we will introduce the fourth parameter, asymptotic angle. There are seven relations between these four parameters. Duality is a key word to understand these relations.


Keywords: spherical conic, asymptotic angle, duality


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Original Research Articles

References

[1] Berger, M., Geometry II Springer-Verlag, Berlin Heidelberg. (1987)
[2] Jennings, G., Geometry with Applications, Springer-Verlag, New York. (1994)