The Extension Principle of Zadeh and Fuzzy Numbers

This chapter presents the Extension Principle of Zadeh, and as the name suggests, it is a method used to extend to fuzzy set theory the typical operations of classical set theory. It gives the framework to calculate the membership degree of elements of a fuzzy set and functions of fuzzy sets, which are the result of operations. Also, in the context of fuzzy sets, the concepts of fuzzy number and fuzzy number arithmetic are introduced.