I came across this cross sign when reading a book. Does anyone know what does this mean in the context of a function?
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1$\begingroup$ Possibly en.wikipedia.org/wiki/Cartesian_product $\endgroup$– zkutchSep 7 at 8:22
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As @zkutch says, this refers to the cartesian product of two sets.
Its definition has to do with sets, not with functions. The formal definition is as follows:
For two sets $A,B$ we define $$A\times B:= \{(a,b)\mid a\in A, b\in B\}$$ Which is the set of all tuples from A and B.
In the context of functions, it might be simpler to think of this as: a function $f:A\times B \rightarrow C$ essentially takes two arguments $a,b$ and spits out a $c$. This will now be written like that:
$$f(a,b)=c$$
Essentially its the same as accepting a tuple $(a,b)$, so you can rest assured this is exactly the formal mathematical definition for set cartesian product here.
