Question

What is the derivative of `y=ln(sec(x))`?

Answer 1

`y'=tan(x)`

Solution

let's `y=ln(f(x))`

differentiating with respective to `x` via Chain Rule,

then, `y'=1/f(x)*f'(x)`,

Similarly following for the given function, `y=ln(sec(x))`

`y'=1/sec(x)*sec(x)tan(x)`

`y'=tan(x)`