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Laplace Transformation - 6G Celicas Forums

Topic #58509 20 posts Started by lubu
lubu
#1
Its 3am in Oz and Im stuck with this gay question:



I know that sin(t) = 1/(s^2 +1) and -t= -1/(s^2) ---> thus = -1/(s^2 +1)^2

but where the fin 2s coming from?? rolleyes.gif

I need a rest.
98% completion---aaRon
99Celica
#2
from what I remember you shouldn't have the variable 's' on top since its a sin function. The 's' comes in when you're using cos. Are you sure you came to that equation correctly? maybe your mistake is earlier. Gl and get some sleep
hongkongnerdboy
#4
im asian

and i cant figure that out
QUOTE(thespacepanda @ Feb 21, 2008 - 4:37 PM) [snapback]644164[/snapback]When I worked for Pizza Hut our store won a health code violation.
96bluevert
#5
Man, I havn't done sin,cos, or tan since HS..sorry can't help you w/ that.
"A true car enthusiast can see the potential in any car"QUOTE (njccmd2002 @ Oct 3, 2008 - 2:01 PM)i rather be a slow turtle in risk of extinction, than a fast locust, that you can see everywhere and need to be terminated.
jason
#6
did you figure it out yet?

if not i can break out my old books n give er a whirl. i used to be good at this stuff like 3 years ago
you know why they put sheep at the edge of a cliff.... that way they push back!(2:27:32 AM) edit: please f*cking work, f*ck, sh*t, piss(2:28:08 AM) edit: that did the trick
99Celica
#7
>
QUOTE (96bluevert @ May 15, 2008 - 4:37 PM) *
>Man, I havn't done sin,cos, or tan since HS..sorry can't help you w/ that.

it's about a 4 year gap of Math education between learning sin,cos,tan and learning Laplace and Fourier transforms. 5 years of nothing but fun and good memories laugh.gif.
lubu
#8
>
QUOTE (99Celica @ May 16, 2008 - 3:48 AM) *
>from what I remember you shouldn't have the variable 's' on top since its a sin function. The 's' comes in when you're using cos. Are you sure you came to that equation correctly? maybe your mistake is earlier. Gl and get some sleep


Actually I need to prove how to get from that to -tsint. But its the Inverse Laplace Transform of Derivatives.

98% completion---aaRon
qatar11
#9
Well... I think you take the Laplace of both sides... should get ride of the Laplace on the left... then you have L (-t sin (t) ) which, after trig identities should expand into something more manageable....
-Mikemjcoury@gmail.comTeam Reynolds StyleCelica BlogCelica WikiIt will take him a moment to realize that he's about to make a 180 degree turn at speed, but you will be ready for it. Brace for the g's, and fast heel-toe work.
qatar11
#11
This is how far I got... I started off with the definition of Leplace, used Integration By Parts, used an Exponential Integration, Used an Euler Identity to reduce the equation...

The only hitch, and it is a big one... I end up with 2t on the top not 2s...,and that t goes to infinity..... maybe I screwed something up somewhere dunno... its been like 5 years since Calc 3.

-Mikemjcoury@gmail.comTeam Reynolds StyleCelica BlogCelica WikiIt will take him a moment to realize that he's about to make a 180 degree turn at speed, but you will be ready for it. Brace for the g's, and fast heel-toe work.
qatar11
#12
I dunno... maybe the integration by parts needs to be done from 0 -> inf as well?

not likely though...
-Mikemjcoury@gmail.comTeam Reynolds StyleCelica BlogCelica WikiIt will take him a moment to realize that he's about to make a 180 degree turn at speed, but you will be ready for it. Brace for the g's, and fast heel-toe work.
qatar11
#13
>
QUOTE (99Celica @ May 15, 2008 - 11:15 PM) *
>Yea thats the method to use. nice work qatar

Ok my turn, i've got this assignment due at 5 tomorrow if anyone wants to do it for me. frown.gif
http://www.engr.ucsb.edu/~me151c/Hw5.pdf

back to work


<Shudders> this is why I am an EE <shudders>
-Mikemjcoury@gmail.comTeam Reynolds StyleCelica BlogCelica WikiIt will take him a moment to realize that he's about to make a 180 degree turn at speed, but you will be ready for it. Brace for the g's, and fast heel-toe work.
lagos
#14
The answer is C.
15PSI - 30MPG - Megasquirt Tuned
qatar11
#15
@Lagos,

Where were you before I spent an hour on this?
-Mikemjcoury@gmail.comTeam Reynolds StyleCelica BlogCelica WikiIt will take him a moment to realize that he's about to make a 180 degree turn at speed, but you will be ready for it. Brace for the g's, and fast heel-toe work.
Consynx
#16
YOUR error is simple
if your demoninator is SUPPOSED to be (s²+1)², you need to have (s²-1)(s²+1) on the bottom.
you are doing (s²+1)(s²) which gives s^4+s². . .


if u still need this solved lemme know, i'll have to go back to the identities, i haven't taken differential equations for 2 years.
but i just graduated!@!!!! Commencement tomorrow, my birthday today! w00t
qatar11
#18
Ya but the work, which is what he has to proved, is left as an exercise.....
though im guessing it is identical to a, where they use t*cost(at)

Bah, I'm too old for this ****...
-Mikemjcoury@gmail.comTeam Reynolds StyleCelica BlogCelica WikiIt will take him a moment to realize that he's about to make a 180 degree turn at speed, but you will be ready for it. Brace for the g's, and fast heel-toe work.
lubu
#19
Ahhh I know what Im forgetting now...



Cheers for all da help...now i know where to go when im stuck! laugh.gif
98% completion---aaRon
Consynx
#20
nvm, followed it.
you just did the top deriv 2nd, so the minus was at the wrong spot, i usually do substitution for stuff now tongue.gif

This post has been edited by Consynx: May 16, 2008 - 11:27 AM
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