Hi chaps and chapesses,
I was wondering if someone could just explain something.
If I have a function which is dependent on $x$, the familiar $f(x)$. Now, if I take the derivative of this, and multiple by $x$ and divide through by $f(x)$.
How does this then become true:
$$ \frac{x}{f(x)}\frac{d(f(x))}{dx}=\frac{d\ln{f(x)}}{d\ln{x}} $$
I'm thinking I'm either a.) tired, b.) stupud or c.) both