Assignment:
Show that given finite sets A_1, A_2,...,A_n, that are pairwise-disjoint, that is A_i intersection A_ j = empty set for all i not equal to j, then their union is a finite set and the cardinality of their union is the sum of the cardinalities of the sets:
#(A_1 union A_2 union...union A_n) = #A_1 + #A_2 +...+ # A_n
* Use that fact that the statement is true for n=2
Provide complete and step by step solution for the question and show calculations and use formulas.