Derivatives Of Log. Functions... HELP!!! Calculus II is a Bitch!
I cant figure out derivatives of Logarithmic functions. Here's an example from my notes.
Problem: Y=ln(x^4(sin^2(x))) Find first derivative. Y= ln(x^4) + ln(sin^2(x)) dx Y= ln(x^4) + ln(sin(x))^2 dx Y=4ln(x) + 2ln(sinx) dx I get here, then I get stuck. Y'= ??? My notes show Y'= (4/x) + (2cos(x))/(sin(x) But I don't see how they got that. I'm pretty sure you have to use chain rule to get this answer, but I don't know I'm just not getting it. :confused: I've even tried some of the online calculus calculators and they come up with different answers then the one from my notes. Thanks for any help. |
My personal opinion. :) Become a psychologist... the math is easier!
Mark |
I'm with Mark, i stopped at Calc 1 for a reason.
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:gay: I made a thread here about hating Calc II last semester. I'll be taking it again next semester. :td:
Edit: and I don't remember how to derive log functions either |
'(ln(x))=1/x
Which gives you 2(sin(x)/x) now go to your law of cos and sin |
lol well once upon a time i could help you but well i don't remember anymore, sorry, what is your major?
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my text book had a log derivatives table with general rules and such... made it so easy that I couldn't possibly do it without my book.... which is at the office, so you are out of luck,
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I should line you out with my roommate, he's a double major, ME and Math.
Took calc 3 and dif-e the same semster, said it was a breeze. He finally has a hard class in school, dif-e 2 is making him hate life. |
Originally Posted by Arkmage
(Post 170348)
my text book had a log derivatives table with general rules and such... made it so easy that I couldn't possibly do it without my book.... which is at the office, so you are out of luck,
I didn't know there was a diff. between x^n and a^x. Of course, there is, and there are diff. rules for each. That was the main thing I was overlooking. My major is Mechanical Engineering. This is my second year and next semester I'll be taking Calculus III, Linear Algerbra, Physics II, and Statics.:ugh2: I'm not exactly looking forward to it. The physics comes easy, but this calculus gets me triped up pretty regularly. Loki, I see that lnx dx = 1/x, but I didn't follow the rest of that. Anyway, I've a few rules to use and so far they're working. |
When i was in calc my book had all of the rules on in the back 2 pages and on the back of the rear cover.
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Originally Posted by cjernigan
(Post 170373)
When i was in calc my book had all of the rules on in the back 2 pages and on the back of the rear cover.
Damn it again. Sure enough, there's 3 pages of formulas back their I could have been using since Cal I. I guess I just never thought to look there. :vash: Oh well, at least I've got all the people on this forum to set me straight.:bigtu: |
Seriously, without those 3 pages i would have failed. Xerox those pages and put them in your notebook, on your wall, your g/fs wall. Just so you know as many of them as possible.
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Originally Posted by cjernigan
(Post 170379)
Seriously, without those 3 pages i would have failed. Xerox those pages and put them in your notebook, on your wall, your g/fs wall. Just so you know as many of them as possible.
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Loki, how do you remember how to do that?
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i hate that shit, I'm doin absolute maxima and minima in calc. I now, dy/dx and limits ftl :td:
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Originally Posted by mazda/nissan
(Post 170386)
i hate that shit, I'm doin absolute maxima and minima in calc. I now, dy/dx and limits ftl :td:
Wait until when (if) you get to the multivariate stuff. Ugh. |
Originally Posted by Ben
(Post 170388)
multivariate stuff
I've also got a lab that uses Maple 11 software with my TA Arnab, but i see it as miataturbo.net time :bigtu: |
you'll need to know that calc when you start taking the heat transfer and control system stuff. it's pretty useful.
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oh goodie, this is what I have to look foward too next year when im a mechanical enginneer in college! woo hoo..
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Stop posting this, it makes not want to go to school
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