A Kannappan-sine subtraction law on semigroups
Let $S$ be a semigroup, $z_0$ a fixed element in $S$ and $σ:S \longrightarrow S$ an involutive automorphism. We determine the complex-valued solutions of Kannappan-sine subtraction law $f(xσ(y)z_0)=f(x)g(y)-f(y)g(x),\; x,y \in S$. As an application we solve the following variant of Kannappan-sine subtraction law viz. $f(xσ(y)z_0)=f(x)g(y)-f(y)g(x)+λg(xσ(y)z_0) ,\; x,y \in S,$ where $λ\in \mathbb{C}^{*}$. The continuous solutions on topological semigroups are given and an example to illustrate the main results is also given.
math.GM↗