Union of Sets

The UNION of two sets A and B is the set of all elements that are in A OR in B (using 'or' in the inclusive sense — an element in both A and B still counts), denoted $A \cup B$. Formally, $A \cup B = \{x/x\in A \text{ or } x\in B\}$. In a Venn diagram, A∪B is the entire region covered by A together with B (Fig. 5.3, Fig. 5.4). For example, if $A=\{x/x \text{ is a prime number less than } 10\} = \{2,3,5,7\}$ and $B=\{x/x\in N, x \text{ is a factor of } 8\}=\{1,2,4,8\}$, then $A\cup B = \{1,2,3,4,5,7,8\}$. …