# Math Help - Derivatives with Trig and Natural Logs

1. ## Derivatives with Trig and Natural Logs

I missed the last couple of lectures because I've been sick, and haven't been able to copy the notes yet. I actually have a quiz on this stuff tomorrow, so if anyone knows of a website that could explain this stuff, then I'd be really grateful.

1) Derivative of f(x)=sin(ln(x))
I obviously don't know what to do...I Googled and found out that the derivative of ln x=1/x, so I tried doing the derivative of sin(1/x), but that didn't work, and I wasn't really sure how to do it.

2) Derivative of (4 - ln(x)) / (2 + ln(x))
Again, no clue how to do this, so any help is appreciated.

2. ## Re: Derivatives with Trig and Natural Logs

Originally Posted by xxStrikeback
I missed the last couple of lectures because I've been sick, and haven't been able to copy the notes yet. I actually have a quiz on this stuff tomorrow, so if anyone knows of a website that could explain this stuff, then I'd be really grateful.

1) Derivative of f(x)=sin(ln(x))
I obviously don't know what to do...I Googled and found out that the derivative of ln x=1/x, so I tried doing the derivative of sin(1/x), but that didn't work, and I wasn't really sure how to do it.
For (1): Use the chain rule.

sin(1/x) is not involved in this problem.

2) Derivative of (4 - ln(x)) / (2 + ln(x))
Use the quotient rule.

3. ## Re: Derivatives with Trig and Natural Logs

Originally Posted by xxStrikeback
I missed the last couple of lectures because I've been sick, and haven't been able to copy the notes yet. I actually have a quiz on this stuff tomorrow, so if anyone knows of a website that could explain this stuff, then I'd be really grateful.

1) Derivative of f(x)=sin(ln(x))
I obviously don't know what to do...I Googled and found out that the derivative of ln x=1/x, so I tried doing the derivative of sin(1/x), but that didn't work, and I wasn't really sure how to do it.

2) Derivative of (4 - ln(x)) / (2 + ln(x))
Again, no clue how to do this, so any help is appreciated.

1. chain rule ... $\frac{d}{dx} \sin{u} = \cos{u} \cdot \frac{du}{dx}$ ... where $u = \ln{x}$