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arXiv · 2210.09111

A d'Alembert type functional equation on semigroups

Youssef Aserrar·Elhoucien Elqorachi
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Abstract

We treat two related trigonometric functional equations on semigroups. First we solve the $\mu$-sine subtraction law \[\mu(y) k(x \sigma(y))=k(x) l(y)-k(y) l(x), \quad x, y \in S,\] for $k, l : S\rightarrow \mathbb{C}$, where $S$ is a semigroup and $\sigma$ an involutive automorphism, $\mu :S\rightarrow \mathbb{C}$ is a multiplicative function such that $\mu (x\sigma (x))=1$ for all $x\in S$, then we determine the complex-valued solutions of the following functional equation \[f(xy) - \mu (y)f(\sigma (y)x) = g(x)h(y),\quad x,y\in S,\] on a larger class of semigroups.

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Youssef Aserrar, Elhoucien Elqorachi. 2022-10-17. A d'Alembert type functional equation on semigroups. https://arxiv.org/abs/2210.09111

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