Just wondering...

L

Lizzie

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Joined
Sep 8, 2005
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317
Ok, here's the problem: I have to find dy/dx for f(x)=cos(3x) ... I'm not a dummy, just for some reason, and maybe I'm just having a blonde moment, I can't seem to get started on this. Any help would be greatly appreciated. I would like to know how to start this, then I can continue and try and solve it :)! -Thanks!
 
Wow, lol. I must have really been having a blonde moment because I was sitting here completely confused and then I suddenly realized what was going on.

So, you're saying that to get dy/dx for f(x)=cos(3x), I take the derivative of cos, which is -sin and keep 3x which makes -sin(3x).

Then, I am supposed to multiply that by the derivative of 3x which is 3.

This means that the answer that I am looking for would be -sin(3x)3?

And, is there a way to simplify this or is it best to leave it alone?
 
Lizzie said:
This means that the answer that I am looking for would be -sin(3x)3?

And, is there a way to simplify this or is it best to leave it alone?
Click to expand...

Usually it looks best if you write it as: -3sin(3x)... but that's it. You derived it perfectly.
 
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