We let
 

and take the formal derivative of 
 
 

Next, we apply the above definition to our function, , to obtain
 
 
 

Now, we expand the expression  as follows
 
 
 

so, we then have that our derivative of  is
 
 
 

To resolve this limit we cleverly rearrange the terms in the numerator as follows
 
 
 

so that we may split the limit into the two parts
 
 
 

Upon rearranging further to
 
 
 

we may then take the above limits to obtain
 
 
 

which gives us our result