Originally Posted by

**Peleus** Hi all,

First things first, what I've seen as the answer for these is described as follows.

$\displaystyle

Dom (f o g) = {x : x \in Domg-and-g(x) \in Dom f}

$

I'm not sure what is meant by the second section though, g(x) in Dom f?

For instance

$\displaystyle f(x) = \sqrt{4 - x^2}$

$\displaystyle g(x) = \ln{x} $

So the dom for f(x) is [-2, 2]

the dom for g(x) is (0, inf]

How does it work fitting into this formula?

$\displaystyle Dom(fog) = x : x \in x > 0 and \ln{x} \in [-2, 2]$

So Dom(fog) = 0 < x < 2 ???

I know this is incorrect, but this is how my logic of applying the formula works.

Anyone who can point out my mistakes or explain it in english a bit better would be appreciated.