About generalization in mathematics (III). On the inclusion and exclusion principle
Gheorghe Miclăuș
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Let A1,A2, …,An be finite sets and m(Ai) denote the number of elements of the set Ai. In this paper we obtain a formula of type ”the inclusion and exclusion principle” (Boole-Sylvester) for finding out the number of elements of the set A1?A2?…?An where A?B =(A\B) ? (B\A) is ”the symmetric difference of the sets A and B”: m(A1?A2?…?An)= = n i=1 m(Ai) ? 2 1?i