## A periodic homeomorphism of the plane.(English)Zbl 0791.58074

West, Thelma (ed.), Continuum theory and dynamical systems. Papers of the conference/workshop on continuum theory and dynamical systems held at Lafayette, LA (USA). New York: Marcel Dekker, Inc.. Lect. Notes Pure Appl. Math. 149, 83-87 (1993).
This short article contains two proofs of a mathematical gem: The homeomorphism of the plane given by $$(x,y)\mapsto (| x| - y,x)$$ is periodic with period 9!
For the entire collection see [Zbl 0777.00054].

### MSC:

 37C25 Fixed points and periodic points of dynamical systems; fixed-point index theory; local dynamics

### Keywords:

periodic homeomorphism; plane