@freemo I agree, I've seen that construction before.
Reading the statement more carefully it looks like it's constructing a map between a set of sets (X is the set of sets x_i) and the union of those same sets.
Which is perfectly reasonable.
I misread the last symbol as an "equal" rather than a "belongs to". My mistake 😅
@freemo
She is shocked because he's clearly confused about the difference between a set and its elements.
Maybe she's a mathematician 😁
Joined Dec 2018
