How do you write log to the base e? I was given a question, find $f'(1)$ of $f(x) = \ln \sqrt{2-x}$.
So I wrote 
$$1/2 \ln (2-x)^{(-1/2)(-1)} = -1/2 \ln (2-x)^{-1/2}$$
$$= -(1/2\ln)/\sqrt{2-x}$$ 
But when I sub in $x = 1$ I get a SYNTAX error, I realised log base e cannot be put in my calculator. I don't know how to put this into my calculator, can anyone help? Thanks!!

$f(x)=\ln(\sqrt{2-x})=\frac{1}{2}\ln(2-x)$, hence $f'(x)=\frac{1}{2}\frac{1}{2-x}\cdot(-1)$.
