The stability of the cosine equation. (English) Zbl 0448.39003


39B99 Functional equations and inequalities
39B52 Functional equations for functions with more general domains and/or ranges
30D05 Functional equations in the complex plane, iteration and composition of analytic functions of one complex variable


Zbl 0086.241
Full Text: DOI


[1] John Baker, J. Lawrence, and F. Zorzitto, The stability of the equation \?(\?+\?)=\?(\?)\?(\?), Proc. Amer. Math. Soc. 74 (1979), no. 2, 242 – 246. · Zbl 0397.39010
[2] D. H. Hyers, On the stability of the linear functional equation, Proc. Nat. Acad. Sci. U. S. A. 27 (1941), 222 – 224. · Zbl 0061.26403
[3] Pl. Kannappan, The functional equation \?(\?\?)+\?(\?\?\(^{-}\)\textonesuperior )=2\?(\?)\?(\?) for groups, Proc. Amer. Math. Soc. 19 (1968), 69 – 74. · Zbl 0169.48102
[4] S. M. Ulam, A collection of mathematical problems, Interscience Tracts in Pure and Applied Mathematics, no. 8, Interscience Publishers, New York-London, 1960. · Zbl 0086.24101
[5] W. Harold Wilson, On certain related functional equations, Bull. Amer. Math. Soc. 26 (1920), no. 7, 300 – 312.
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