t-Lower level set and t-upper level set of an intuitionistic fuzzy set

In this paper we give the definitions of t-lower level set (Lt(A)) and t-upper level set (Ut(A)) of an Intuitionistic fuzzy set. [1] A t-lower level set is defined by giving a lower boundary on μA(x) + νA(x). A t-upper level set is defined by giving an upper boundary on μA(x) + νA(x). If A is an Intuitionistic fuzzy set of X, then Lt(A) and Ut(A) are subsets of X. In this paper we give some theorems by using t-lower level sets and t-upper level sets and prove them.