- #1

Joe_K

- 33

- 0

## Homework Statement

Find the Derivative of:

(ln(cos4x)) / 12x^2

## Homework Equations

y' ln(x) = 1/x

## The Attempt at a Solution

I have determined the correct answer, but I am still confused as to how I came to the solution. Starting with the numerator, the derivative of cos is -sin. This would produce ln(-4sin(4x)) in the numerator. Now, to take the derivative of the natural log, I would do ln(x)= 1/x, correct? So 1/-4sin(4x)?

Why does the final numerator come out to -4tan(4x)? I know I am missing a basic rule or overlooking something... but why does it become tangent?

Thank you