sandy524
find the derivative of f(x) = 3x cos 6x .
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Mimi_x3
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\[\frac{d}{dx}3xcos6x\]
Do you know the product rule?
sandy524
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yes
Mimi_x3
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So, what have you done?
sandy524
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but how would i use it in this case
Mimi_x3
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Where are you having problems?
sandy524
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may someone please show me step by step how to do this. my professor sucks and is currently being investigated by the math dept here because of it so yeah...
tinagca
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Here is a great site to help you with your math! www. mathway.com! :)
tinagca
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That site will provide you with a step by step! :D
sandy524
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mathway is not credible
Mimi_x3
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Well, have you atleast tried it?
tinagca
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How i learn a lot from that site...
tinagca
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You just have to sign up to get the step by step part!! :) It helps me a ton...
sandy524
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i have missed many questions from its wrong answers. wolframalpha is more reliable
tinagca
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Okay. maybe you just type them in wrong... it always helps me :D
tinagca
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I dont use it for tests though... i use it for help... you use it for tests?
sandy524
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okay sure but anyways thanks bye. now back to the question i need help with
Mimi_x3
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@tinagca: Please don't divert people to another site; when someone is trying to help them.
tinagca
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Mkay! later :D
tinagca
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I was trying to give her a step by step site :o
Mimi_x3
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That was retarded; interjecting out of the blue.
sandy524
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please folks i really need help the bantering can be spared
tinagca
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Oh shut up. like seriously i was trying to help then you guys started being rude. So whatever, a simple thank you and just saying " Oh i already tried that site" would have been fine.
zepdrix
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|dw:1350314820570:dw|
sandy524
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thank you zepdrix u are always so helpful
zepdrix
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so do it piece by piece :) We have a (3x)', what is the derivative of 3x? :D
sandy524
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simply 3
zepdrix
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ok cool, so the first term will simplify to (3)(cos6x).
Hmm now we have a (cos6x)' on the right side.
We'll take the derivative of the outermost function (cosine)
Then "chain" (multiply by the derivative of the inside (6x)' )
So whats the derivative of cos6x? :D
sandy524
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-6sin(6x)
sandy524
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right
zepdrix
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Yay sandy \c:/
tinagca
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You should give @zepdrix a medal @sandy524 ...i mean, that was a great answer!
zepdrix
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lol tina c:
tinagca
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:) I gave you a medal! :D
sandy524
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ok so after that what do we do
zepdrix
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Just combine the pieces together and simplify :D
So far we've figured out that the derivative is
(3)(cos6x) + (3x)(-6sin6x)
=3cos6x -18xsin6x
Make sense? :D