References
- J. Aczél, Lectures on Functional Equations and their Applications, Academic Press, New York, 1966.
- J. Aczél and J. Dhombres, Functional Equations in Several Variables. With Applications to Mathematics, Information Theory and to the Natural and Social Sciences, Encyclopedia Math. Appl., 31, Cambridge University Press, Cambridge, 1989.
- O. Ajebbar and E. Elqorachi, The Cosine-Sine functional equation on a semigroup with an involutive automorphism, Aequationes Math. 91 (2017), no. 6, 1115–1146.
- O. Ajebbar and E. Elqorachi, Solutions and stability of trigonometric functional equations on an amenable group with an involutive automorphism, Commun. Korean Math. Soc. 34 (2019), no. 1, 55–82. DOI: 10.4134/CKMS.C170487
- Y. Aserrar and E. Elqorachi, A d’Alembert type functional equation on semigroups, arXiv preprint, 2022. Available at arXiv: 2210.09111
- Y. Aserrar and E. Elqorachi, Five trigonometric addition laws on semigroups, arXiv preprint, 2022. Available at arXiv: 2210.06181
- J.K. Chung, Pl. Kannappan, and C.T. Ng, A generalization of the Cosine-Sine functional equation on groups, Linear Algebra Appl. 66 (1985), 259–277.
- B. Ebanks, The cosine and sine addition and subtraction formulas on semigroups, Acta Math. Hungar. 165 (2021), no. 2, 337–354. DOI: 10.1007/s10474-021-01167-1
- B. Ebanks, Around the sine addition law and d’Alembert’s equation on semigroups, Results Math. 77 (2022), no. 1, Paper No. 11, 14 pp. DOI: 10.1007/s00025-021-01548-6
- Pl. Kannappan, Functional Equations and Inequalities with Applications, Springer Monogr. Math., Springer, New York, 2009. DOI: 10.1007/987-0-387-89492-8
- T.A. Poulsen and H. Stetkær, On the trigonometric subtraction and addition formulas, Aequationes Math. 59 (2000), no. 1-2, 84–92.
- H. Stetkær, Functional Equations on Groups, World Scientific Publishing Co., Singapore, 2013.
- E. Vincze, Eine allgemeinere Methode in der Theorie der Funktionalgleichungen. II, Publ. Math. Debrecen 9 (1962), 314–323.