New algorithms for trapezoidal approximation of fuzzy numbers preserving the expected interval

Fuzzy number approximation by trapezoidal fuzzy numbers which preserves the expected interval is discussed. New algorithms for cal-culating the proper approximations are proposed. It is shown that the adequate approximation opera-tor is chosen with respect both to the global spread of a fuzzy number and the size of possible asymmetry between the spread of the left-hand and right-hand part of a fuzzy num-ber