Bulletin of the
Korean Mathematical Society
BKMS

ISSN(Print) 1015-8634 ISSN(Online) 2234-3016

Article

HOME ALL ARTICLES View

Bull. Korean Math. Soc. 2023; 60(2): 507-514

Online first article March 24, 2023      Printed March 31, 2023

https://doi.org/10.4134/BKMS.b220246

Copyright © The Korean Mathematical Society.

Hyperbolic and spherical power of a circle

Young Wook Kim, Sung-Eun Koh, Hyung Yong Lee, Heayong Shin, Seong-Deog Yang

Korea University; Konkuk University; Korea University; Chung-Ang University; Korea University

Abstract

Suppose that a line passing through a given point $P$ intersects a given circle $\mathcal{C}$ at $Q$ and $R$ in the Euclidean plane. It is well known that $|PQ||PR|$ is independent of the choice of the line as long as the line meets the circle at two points. It is also known that similar properties hold in the 2-sphere and in the hyperbolic plane. New proofs for the similar properties in the 2-sphere and in the hyperbolic plane are given.

Keywords: Power of a circle, hyperbolic plane, sphere, conformal metric

MSC numbers: 53A35

Supported by: Heayong Shin was supported by NRF 2014R1A2A2A01007324, Sung-Eun Koh by NRF 2020R1A2C1A01003666 and Seong-Deog Yang by NRF 2012-042530.