# What set operation is this?

Given two sets $A = \{\{1\} , \{2 , 6\} \}$ and $B = \{\{2\} , \{3\} , \{4 , 5\} \}$, what set operation can produce $$C = \{ \{ 1 , 2 \} , \{ 1 , 3 \} , \{ 1 , 4 , 5 \} , \{ 2 , 6 , 2 \} , \{ 2 , 6 , 3 \} , \{ 2 , 6 , 4 , 5 \}\}?$$

The set $C$ is gained by Cartesian product firstly, then two elements of each pair are combined by union. I wonder whether there is a more simple solution?

• I’d describe $C$ simply as $\{a\cup b:a\in A\land b\in B\}$, which is of course equivalent to your $\{a\cup b:\langle a,b\rangle\in A\times B\}$. I see nothing simpler. – Brian M. Scott Apr 1 '12 at 21:44
• If were allowed to make up names, I call it "Cartesian union"! – user2468 Apr 1 '12 at 23:32
• Thanks a lot, Brain M. Scott and J.D.. Why not Kejia Union :-D – 象嘉道 Apr 2 '12 at 17:10

## 1 Answer

Converting comment to answer to get this off the Unanswered list:

I’d describe $C$ simply as $\{a\cup b:a\in A\land b\in B\}$, which is of course equivalent to your $\{a\cup b:\langle a,b\rangle \in A\times B\}$. I see nothing simpler.