# Calculating Strange Union

by xx01   Last Updated August 01, 2020 11:20 AM - source

Hello everyone assume that we set $$A$$ = {{1 ,2} , {2 ,3} ,{4 ,3}}

so what is $$\cup_{B \in A} (B)$$?

Tags :

$$\{1,2\}\cup \{2,3\} \cup \{4,3\}$$..

Coward
August 01, 2020 10:51 AM

Here The elements of $$A$$ are $$\{1,2\}, \{2,3\}, \{4,3\}$$. So the union of elements of $$A$$ is:

$$\cup_{B\in A} B = \{1,2\} \cup \{2,3\} \cup \{4,3\}.$$

Uncool
August 01, 2020 10:56 AM

I surmise that this was a trick question. The intention is for the student to realize that the union of all elements of a specific set is the specific set itself, without any regard to what the elements actually are.

Subsequent comments by Aurelio and Coward have suggested that I am mistaken. I may well be mistaken, but I'm just not seeing it yet.

Coward: In response to your comment, could you please provide a counter example?

Aurelio: In response to your counter example, perhaps I'm missing something here. In your counter example, it does seem to me that $$\bigcup_{b \in A} \;=\; A.$$ Please explain if you think that I am mistaken.

user2661923
August 01, 2020 10:58 AM