Parameters from parameters

If I have a function and then set the parameters if I then have a function within that function can I use the parametes of the first function to set parameters for the second function.

[AS]
function thing(a,b){
//do something
if(_root.whatever== true){
function secondThing(copyA,copyB)
}
}
[/AS]
Or must I just create variables for it and then just use them?
[AS]
function thing(a,b){
this.a = a
this.b = b
//do something
if(_root.whatever== true){
function secondThing(this.a,this.b)
}
}
[/AS]
If you know of a better way then feel free to chuck that at me too :D.
This shouldn’t be too tasking for you lol.
Cheers,
Mr_Beef.