EDB — 23W

[23W]The notation in [026]↺↻ differs from the usual one, which is ${\bigcup }_{i\in I}{C}_i$, where $I$ is a non-empty family of indices and $C_i$ are sets; as seen in [1Y2]↺↻.

How can you define ${\bigcup }_{i\in I}{C}_i$ using the axiom of union presented [026]↺↻? (Sugg. re-read the note [01M]↺↻)

Eventually you should obtain