A new point of view to the inclusion — Exclusion principle

Applying two definitions for the union of IF-events P. Grzegorzewski ([5]) gave two characterizatios of the inclusion-exclusion principle for IF-events (= intuitionistic fuzzy sets in Atanassov's sense). In this paper we consider such operations that the Grzegozrewski approach is a very special case. Our proof is new in some sense.