EDB — 24P

Exercises

1. [24P]Let \(I,C_ i\) as in [1Y2]↺↻ and let \(A\) be a set; prove that

   \[ ⋃_{i∈ I}C_ i \subseteq A \]

   if and only if 

   \[ \forall {i∈ I} , ~ C_ i \subseteq A~ . \]