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Calculus help please

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walcott
Posts: 319 - Karma: 39
i really desperate to solve these problems. if someone even did one problem it would be great

y=sin(^-1)x solve terms of x

y=cos^(-1)x^3 solve in terms of x

y=3lnx find y'

y=lnx^3 find y'

y=(cosx)^4x find y'
May 11 2011 4:53PM
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a.wall
Posts: 339 - Karma: 30
lol
May 11 2011 4:59PM
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Anathema
Posts: 21048 - Karma: 5,061
3. 3/x

i remember that much from just looking at it. the derivative of ln x is just 1/x..
May 11 2011 5:04PM
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huge-go
Posts: 1451 - Karma: 33
Completely forgot what it means to solve in terms of x.
the last 3 are pretty simple though. Forgot what the derivative of lnx, I think it's e^x, in which case y' for y=3lnx is just 3(e^x). Second last one is the same as that one I think, because lnx^3=3lnx. Last one is chain rule and I don't remember any of the derivatives of trig functions.
May 11 2011 5:05PM
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Anathema
Posts: 21048 - Karma: 5,061
oh, and that would make (4) the same thing, because ln x^3 = 3 ln x , which is the same as (3), so again 3/x is your answer

i think
May 11 2011 5:08PM
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huge-go
Posts: 1451 - Karma: 33
fuck, I failed. I still think the answer to the third and fourth ones is the same though.
May 11 2011 5:09PM
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Anathema
Posts: 21048 - Karma: 5,061
well the derivative of e^x is just e^x, so it couldnt be the derivative of ln x


May 11 2011 5:12PM
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los.pinguinos
Posts: 555 - Karma: 34
1. 45
2. 43.77
3.887.6
dont know rest
May 11 2011 5:15PM
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walcott
Posts: 319 - Karma: 39
thanks for the help, i've been lost in that class since day 1

May 11 2011 5:38PM
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icon1234
Posts: 3081 - Karma: 1,475
Dude open your textbook and look at the formulas they will tell you exactly how to do it and you will actually learn something. Also these are all pretty damn easy, I bet they will have exact replica's of these problems but with different numbers...
May 11 2011 5:39PM
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john.stossel
Posts: 943 - Karma: 5
bomber bob is right. we have enough fucking lawyers in this country already. we dont need more.. so learn math so you can do things relevant to helping society (designing buildings, saving peoples lives etc) as opposed to what lawyers do (take money from one place and put it in another
May 11 2011 6:52PM
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CassiusClay
Posts: 1757 - Karma: 2
Those aren't too tough, but here are some ideas on how to help learn it yourself: 1. your textbook, 2. youtube videos (yes, nerds make all kinds of math videos), 3. google, 4. wolfram
May 11 2011 6:54PM
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airic
Posts: 720 - Karma: 16
How to solve # 4:

Step 1) Take the natural log. of both sides

Step 2) differentiate both sides with respect to x

Step 3) isolate y'

ANswer:

y'= y*(ln(cosx) -x*tan(x))
May 11 2011 7:38PM
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ECB
Posts: 6991 - Karma: 622
Here was my solution to calc:

Drop it
May 11 2011 7:39PM
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airic
Posts: 720 - Karma: 16
Sorry, the I forgot the factor of 4:

ANSWER: y'= 4*y*(ln(cosx) -x*tan(x))
May 11 2011 7:39PM
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family_vacation
Posts: 6200 - Karma: 7,840
Actually learn how though, no point in just coasting if want to get something out of the class while not being raped by tests.

Here, your math class troubles are over.
http://www.khanacademy.org/#calculus
May 11 2011 7:45PM
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huge-go
Posts: 1451 - Karma: 33
I don't remember any of the derivatives, other than the really simple ones, just like the rules and shit(product rule, chain rule etc..). I'm surprised I remember even those after a full year off from school though. Gonna have to brush up so the start of engineering doesn't rape me in the butt.
May 11 2011 7:47PM
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tomahawk
Posts: 2006 - Karma: 53
are 3-5 y prime or derivative problems.

thats key.

but if you're solving for y prime you'll need to take the natural log of y and the other side as well.

this is calc 1 or 2? i cant remember.

but use your textbook. the formulas are so easy for these problems. just cant remember them.
May 11 2011 8:28PM
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DrZoidberg
Posts: 5675 - Karma: 4,268
y' = y prime =derivative

Derivative of arcsine is 1/sqrt(1-x^2), and memorize that. It comes up a lot if you go further in calc.

Also, wolframalpha.com. Type in d/dx, or your favorite derivative notation, and then the function. It even shows steps.

May 11 2011 9:32PM
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n_b
Posts: 580 - Karma: 68
wow.
May 11 2011 10:07PM
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.Emerson.
Posts: 1548 - Karma: 16
3. as stated earlier is 3/x. Product rule: O(lnx)+3(1/x) because ' of lnx=1/x. therefore y'=3/x


4. I don't know if this is supoosed to be done with the chain rule or implicit differentiation, I shall do both.

ID: lny=3lnx then (1/y)(y')=3(1/x).
y'=(ln(x)^3)(3/x)
CR: y'=(3ln(x)^2)(1/x)

5. lny=4x(lncos(x)).
(1/y)(y')=4lncos(x) + 4x(1/cosx)(-sinx because of chain rule for lncosx).
(1/y)y'=4lncos(x) + 4x(-tanx)
y'=(cos(x)^4x)4(lncos(x) -xtan(x))



inb4 I did everything wrong and I have my final tomorrow
May 11 2011 11:45PM
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alexat955
Posts: 2732 - Karma: 112
learn implicit differentiation. I would help you if I wasn't on my phone but imnot typing all that shit out with just my thumbs
May 11 2011 11:46PM
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tall_t
Posts: 1036 - Karma: 15
im on the same page as you OP
May 11 2011 11:51PM
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