Q: How can 
and 
be approximated for ``small'' values of
, 
compared to x?
(b1)
where 
For 
For also small 
, then:
Example: 
Exact 
For : 
Exact 
(b2) Approximation of ``l''
So for 
then
the terms
are smaller than 1 and
For example : 
So finally 
for 
Example: 
Exact l=1.1045