# What does x sign mean in functions

I came across this cross sign when reading a book. Does anyone know what does this mean in the context of a function?

• Sep 7, 2021 at 8:22

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.