Abstract
Our main result is the solution of the functional equation \(f(x\sigma (y))+h(\tau (y)x)=2f(x)k(y)\) for complex-valued functions f, h, k on monoids generated by their squares. Here \(\sigma \) and \(\tau \) are involutive automorphisms of the monoid.
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Ebanks, B. Some trigonometric functional equations on monoids generated by their squares. Aequat. Math. 95, 383–391 (2021). https://doi.org/10.1007/s00010-020-00730-5
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DOI: https://doi.org/10.1007/s00010-020-00730-5