Thank you Alan,
How did you do the initial expansion? What kind of an expansion is that?
Thanks Alan but worry too much, I don't understand expansions much. :(
I only know the binomial expansion.
I just wondered :/
I can follow most of that but you lost me at $$O(x^2)$$ and what happened to all the other powers of x?
Only answer is you feel enthused because this stuff is really over my head. I couldn't reproduce it. :(
Rather than writing all the other terms involving x2, x3 etc. I've written O(x2), meaning terms of order x2 and smaller ("smaller" because we are going to make x go to 0, so x4, x3 etc. are going to be smaller than x2). The important thing is that all these other terms will be multiples of xn, where n>1, so that when they are divided by x they are still mutiples of powers of x and hence vanish in the limit as x tends to 0.