Summary Since isosceles triangular and trapezoidal membership functions [4] are easy to manage, they were applied various fuzzy approximate reasoning [10], [13], [14]. The centroids of mentioned in this article [16], [9] formalized [11] [12]. Some propositions the composition mapping ( f + · g , or +* using Mizar formalism, where a ne mappings), proved following [3], [15]. Then different notati...