1. ## Derivative

What is the derivative of the following function ?

2. Originally Posted by totalnewbie
What is the derivative of the following function ?
Use the chain rule:

If:

$
y=f(g(x))
$

then:

$
\frac{dy}{dx}=f'(g(x))\ g'(x)
$

In this case $f(u)=\ln(u)$ and $g(u)=u^2+1$, so:

$
\frac{d}{dx}\ \ln(x^2+1) = \frac{1}{x^2+1}\ 2x=\frac{2x}{x^2+1}
$

RonL