"Brian,
> There are at least three errors there: a missing comma, a
> missing right curly brace, and missing arguments on the name
> of the collection of sets. You want:
>
> sum{|B(x, p, q)| : B(x, p, q) in script-B(x, J)}
>
> However, you don't actually need all of that clutter:
>
> sum{|B| : B in script-B(x, J)}
>
> says exactly the same thing.
>
>> And if I want the union of all B(x,p,q), what then?
>
> Just stick a union sign in front of script-B(x, J). I
> suppose that in LaTeX this is something like
>
> \bigcup \mathcal{B}(x, J)
For union I have always been using \cup; is there something I need to know
about the distinction between \cup and \bigcup?
So for the cardinality of that union of sets, I can assume that the union
is
itself a set and I write |\bigcup script-B(x, J)|?
With thanks.
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