Stability of a system of generalized trigonometric equations. (English) Zbl 0842.39011
The author shows some addition formulas for generalized trigonometric functions and by applying functional equation methods the Hyers-Ulam stability of these formulas is studied. Some connections with the theory of characters on groups are investigated. The proofs are elegant.
Reviewer: C.Alsina (Barcelona)
MSC:
39B62 | Functional inequalities, including subadditivity, convexity, etc. |
39B72 | Systems of functional equations and inequalities |