Superstability of approximate cosine type functions on the monoid R2

• Autores: Belaid Bouikhalene, Elhoucien Elqorachi, A. Charifi
• Localización: Extracta mathematicae, ISSN-e 0213-8743, Vol. 27, Nº 2, 2012, págs. 155-162
• Idioma: inglés
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• Resumen

  • In this paper, we study the superstability problem for the cosine type functional equation f(x1x2; x1y2 + x2y1) + f(x1x2; y1x2 .. x1y2) = 2f(x1; y1)f(x2; y2) on the commutative monoid (R2, X). As a result we obtain cosine type functions satisfying the equation approximately.