# What Does these symbol mean. [duplicate]

It's very simple. I don't know how to interpret these symbols (highlighted in image below) in the context of this example. So, can someone tell me how to read them?

example

## marked as duplicate by Community♦Oct 20 '18 at 13:59

• e.g. $\bigcup_{j=1}^3A_j$ stands for $A_1\cup A_2\cup A_3$. – drhab Oct 20 '18 at 13:54

• $$\bigcup_i A_i$$ the UNION of the sets $$A_i$$ that is $$A_1\cup A_2\cup\ldots\cup A_n$$
• $$\bigcap_i A_i$$ the INTERSECTION of the sets $$A_i$$ that is
$$A_1\cap A_2\cap\ldots\cap A_n$$