Fuzzy differential equations and Zadeh´s extension principle

In this article we show the importance of the class of fuzzy differential equations where the right hand side of the equation is a fuzzy function generated by applying Zadeh´s extension principle. Through concrete examples, we show that fuzzy functions obtained by applying Zadeh´s extension principle are more appropriate than fuzzy functions obtained by using the usual fuzzy interval arithmetic (R.E. Moore´s interval arithmetic on alpha-levels).