Answer
$y'=tan(x)$
Work Step by Step
Start with the function: $y=ln(sec(x))$.
Use chain rule to differentiate: $y'=\frac{1}{sec(x)}*\frac{d}{x}(sec(x))$.
Differentiate $sec(x)$ and plug in: $y' = \frac{sex(x)tan(x)}{sec(x)}$.
Simplify to arrive at the answer: $y'=tan(x)$.
