## swin2013 2 years ago derivative?

1. swin2013

$\ln(\cos(w-1))$

2. calculusfunctions

To take the derivative of the natural logarithm function, divide the derivative of the argument function by the argument function. Thus$\frac{ d(\ln f(x)) }{ x }=\frac{ f \prime(x) }{ f(x) }$Do you understand?

3. swin2013

so it's 1/cos(w-1) * -sin(w-1) *1?

4. calculusfunctions

Sorry, that should be dx in the first denominator.

5. calculusfunctions

YES!!

6. calculusfunctions

$\frac{ d(\ln (\cos (w -1)) }{ dx }=\frac{ -\sin (w -1) }{ \cos (w -1) }=-\tan (w -1)$Understand?

7. calculusfunctions

@swin2013 I asked if you understood.

8. swin2013

yes i do sorry, i was working on another problem :)

9. calculusfunctions

No worries!