I have a question about the notation of integrals, I apologize if it is stupid. Usually the notation of integrals goes like this:
$$ \ \int f(x) dx \ $$
But let's say that for whatever reason we have chosen to name a variable something other than $x$ - for example, $a$. Would then the notation change to this:
$$ \ \int f(a) da \ $$
Or would the $dx$ term remain unchanged:
$$ \ \int f(a) dx \ $$
or some third option?