On the stability of the pexiderized trigonometric functional equation

The aim of this paper is to investigate the superstability problem of the cosine( d'Alembert), the Wilson, and the sine functional equation from the pexiderized trigonometric functional equation (T-gh) under the condition: vertical bar f(x+y)-f(x-y)-2g(x)h(y)vertical bar <= phi (x) or phi(y), and also will investigated the stability of the Jensen type functional equation (J(y)) under the condition: vertical bar f(x+y)-f(x-y)-2f(y)vertical bar <= phi (x,y). (c) 2008 Elsevier Inc, All rights reserved.