Fixed Point Theory and Applications
Volume 2008 (2008), Article ID 945010, 7 pages
Research Article

A Fixed Point Approach to the Stability of a Functional Equation of the Spiral of Theodorus

Soon-Mo Jung1 and John Michael Rassias2

1Mathematics Section, College of Science and Technology, Hong-Ik University, 339-701 Chochiwon, South Korea
2Mathematics Section, Pedagogical Department, National and Capodistrian University of Athens, 4 Agamemnonos Street, Aghia Paraskevi, Attikis, 15342 Athens, Greece

Received 2 April 2008; Accepted 26 June 2008

Academic Editor: Fabio Zanolin

Copyright © 2008 Soon-Mo Jung and John Michael Rassias. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Cădariu and Radu applied the fixed point method to the investigation of Cauchy and Jensen functional equations. In this paper, we adopt the idea of Cădariu and Radu to prove the stability of a functional equation of the spiral of Theodorus, f(x+1)=(1+i/x+1)f(x).