
Blake_Shroom
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Brain fart! Need math help! Nerds come please :)
#11303665  10/23/09 01:27 AM (7 years, 11 months ago) 


So in calculus we have to find the derivative. I know how to do that, but i completely forgot how to work with sin/cos/tan, ect.
How can i make Cos(3x)2 (the 2 is squaring the 3x, I dont know how to make a little 2 lol)
So how can i make something like that, end up like 2cos3x?(thats just an example)
I need to figure out what the 3x does to the equation and same with the square. I think the squre can be changed to the front of the equation like 2cos(3x) but i'm not really sure.
THanks for the help!

dkamp18
The Real World
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Re: Brain fart! Need math help! Nerds come please :) [Re: Blake_Shroom]
#11303813  10/23/09 02:01 AM (7 years, 11 months ago) 


sin,cos,tan^1
if i understood your question right. not sure i did, lol, sorry.

pwnasaurus
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Re: Brain fart! Need math help! Nerds come please :) [Re: Blake_Shroom]
#11303820  10/23/09 02:04 AM (7 years, 11 months ago) 


Quote:
Blake_Shroom said: So in calculus we have to find the derivative. I know how to do that, but i completely forgot how to work with sin/cos/tan, ect.
How can i make Cos(3x)2 (the 2 is squaring the 3x, I dont know how to make a little 2 lol)
So how can i make something like that, end up like 2cos3x?(thats just an example)
I need to figure out what the 3x does to the equation and same with the square. I think the squre can be changed to the front of the equation like 2cos(3x) but i'm not really sure.
THanks for the help!
dy/dx of y = cos(3x)^2 (the '^' means to the power of) is:
2cos(3x)*sin(3x)*3 = 6cos(3x)*sin(3x)
This is due to the chain rule. If you need a further explanation let me know.

Neuron
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Re: Brain fart! Need math help! Nerds come please :) [Re: pwnasaurus]
#11303828  10/23/09 02:08 AM (7 years, 11 months ago) 


pwnasaurus is so sexy with his red lipstix and math equations


pwnasaurus
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Re: Brain fart! Need math help! Nerds come please :) [Re: Neuron]
#11303847  10/23/09 02:14 AM (7 years, 11 months ago) 


No lipstick Neuron  my lips are just naturally sexy as fuck

Blake_Shroom
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Re: Brain fart! Need math help! Nerds come please :) [Re: pwnasaurus]
#11303880  10/23/09 02:24 AM (7 years, 11 months ago) 


Ahhh thanks man. like i said i had a brain fart and forgot lol. Thanks
and since you are so good at this, and so nice , wanna help me with another?
Evaluate the derivative of y=4sinxx @ x=(pi) (dont have to pi symbol on my keyboard lol)
thanks a ton man!

pwnasaurus
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Re: Brain fart! Need math help! Nerds come please :) [Re: Blake_Shroom]
#11303913  10/23/09 02:34 AM (7 years, 11 months ago) 


dy/dx = 4cos(x)  1 dy/dx @ pi = 4cos(pi)  1 = 4(1)  1 = 5

Neuron
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Re: Brain fart! Need math help! Nerds come please :) [Re: pwnasaurus]
#11303925  10/23/09 02:37 AM (7 years, 11 months ago) 


I wonder who is better at math, pwnasaurus or Coaster?


Blake_Shroom
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Re: Brain fart! Need math help! Nerds come please :) [Re: Neuron]
#11303954  10/23/09 02:43 AM (7 years, 11 months ago) 


you're a life saver man.
How about this one? Determine the points at which y=X^42x^2+2 has a horizontal line.
Or Find the derivative of y=cos^2*3x (I dont know what to do when just the cosine is squared)
Or find the derivative y=cos(3x)^2 (all these problems are the same setup, just a few things that tweek the outcome. Like i said, i forgot all of these rules. maybe a lil too much booze lol)
Thank you sooooo much for all of the help! I got a huge test tomorrow

DieCommie
Registered: 12/11/03
Posts: 29,008

Re: Brain fart! Need math help! Nerds come please :) [Re: Neuron]
#11303981  10/23/09 02:51 AM (7 years, 11 months ago) 


Quote:
Neuron said: I wonder who is better at math, pwnasaurus or Coaster?
Easy question!

Neuron
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Re: Brain fart! Need math help! Nerds come please :) [Re: DieCommie]
#11303993  10/23/09 02:55 AM (7 years, 11 months ago) 


Quote:
DieCommie said:
Quote:
Neuron said: I wonder who is better at math, pwnasaurus or Coaster?
Easy question!
lol, I love it.
Even though Coast has a bachelors in mathematics, methinks he does 2 many drugs to retain all the mathematical rules/theorems.


DieCommie
Registered: 12/11/03
Posts: 29,008

Re: Brain fart! Need math help! Nerds come please :) [Re: Neuron]
#11303995  10/23/09 02:56 AM (7 years, 11 months ago) 


Yea, Ive seen plenty of people get degrees and still not know shit in their subject.

pwnasaurus
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Re: Brain fart! Need math help! Nerds come please :) [Re: Blake_Shroom]
#11304005  10/23/09 03:00 AM (7 years, 11 months ago) 


Quote:
Blake_Shroom said: you're a life saver man.
How about this one? Determine the points at which y=X^42x^2+2 has a horizontal line.
Or Find the derivative of y=cos^2*3x (I dont know what to do when just the cosine is squared)
Or find the derivative y=cos(3x)^2 (all these problems are the same setup, just a few things that tweek the outcome. Like i said, i forgot all of these rules. maybe a lil too much booze lol)
Thank you sooooo much for all of the help! I got a huge test tomorrow
y = x^42x^2+2
dy/dx = 4x^3  2*2x
Horizontal line would be when dy/dx = 0 so:
0 = 4x^3  4x = x^3  x = x(x^2  1) = x(x1)(x+1) x = 0, 1, 1
For all three of those values the derivative is a horizontal line.
The second one doesn't make sense. You can't "just square cos".
However, there is a convention, where if you write
cos^2(x) = (cos(x))^2. So chain rule once again.

pwnasaurus
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Re: Brain fart! Need math help! Nerds come please :) [Re: pwnasaurus]
#11304013  10/23/09 03:02 AM (7 years, 11 months ago) 


I'm going to bed now though, as I have TWO tests tomorrow and an assignment to do. Good luck buddy. Night shroomery

starfirex
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Re: Brain fart! Need math help! Nerds come please :) [Re: Blake_Shroom]
#11304502  10/23/09 07:51 AM (7 years, 11 months ago) 


expand the cos(3x^2)with the identity cos(u)=[{e^iu)+e^(iu)}]/2 where i is the operator square root of negative one and e is the base of the natural logarithm. I believe this is a variant of euler's identity but I'm an engineer and we do all this on computer now rather than fuck with formulas.
 If the neighbors complain 'cause the music is too loud, turn it up so you can't hear them bitch. ~ I'm blowing my mind....one asskicking trip at a time....

pwnasaurus
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Re: Brain fart! Need math help! Nerds come please :) [Re: starfirex]
#11304539  10/23/09 08:12 AM (7 years, 11 months ago) 


Quote:
starfirex said: expand the cos(3x^2)with the identity cos(u)=[{e^iu)+e^(iu)}]/2 where i is the operator square root of negative one and e is the base of the natural logarithm. I believe this is a variant of euler's identity but I'm an engineer and we do all this on computer now rather than fuck with formulas.
This is complex analysis, and is not related to his calc 1 course. Definitely don't do this.

starfirex
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Re: Brain fart! Need math help! Nerds come please :) [Re: pwnasaurus]
#11304551  10/23/09 08:19 AM (7 years, 11 months ago) 


This is too in calc one, if I remember correctly. You learn the identities for log and ln derivitaves in calc 1. But yes, you will also get it again and have to do the proofs in complex variable course.
 If the neighbors complain 'cause the music is too loud, turn it up so you can't hear them bitch. ~ I'm blowing my mind....one asskicking trip at a time....

DieCommie
Registered: 12/11/03
Posts: 29,008

Re: Brain fart! Need math help! Nerds come please :) [Re: pwnasaurus]
#11305144  10/23/09 11:34 AM (7 years, 11 months ago) 


Quote:
pwnasaurus said:
Quote:
starfirex said: expand the cos(3x^2)with the identity cos(u)=[{e^iu)+e^(iu)}]/2 where i is the operator square root of negative one and e is the base of the natural logarithm. I believe this is a variant of euler's identity but I'm an engineer and we do all this on computer now rather than fuck with formulas.
This is complex analysis, and is not related to his calc 1 course. Definitely don't do this.
Seriously, why the fuck would anybody do that. No engineer would take a simple derivative by doing that.

starfirex
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Re: Brain fart! Need math help! Nerds come please :) [Re: DieCommie]
#11305251  10/23/09 12:09 PM (7 years, 11 months ago) 


No engineer takes a derivative of anything. That's why I said we use computers.
 If the neighbors complain 'cause the music is too loud, turn it up so you can't hear them bitch. ~ I'm blowing my mind....one asskicking trip at a time....

DieCommie
Registered: 12/11/03
Posts: 29,008

Re: Brain fart! Need math help! Nerds come please :) [Re: starfirex]
#11305277  10/23/09 12:16 PM (7 years, 11 months ago) 


What exactly do you engineer? An engineer who cant take the derivative of a simple sine function isnt much of an engineer IMO.

