 Laplace Transformation, im stuck!! |
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 May 15, 2008 - 2:05 PM
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 Enthusiast  Joined Apr 2, '07 From Great Western Plateau Currently Offline Reputation: 9 (100%)  |
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??  I need a rest. --------------------  98% completion --- aaRon |
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May 15, 2008 - 2:48 PM
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 Enthusiast Joined Nov 1, '07 From Santa Barbara, CA Currently Offline Reputation: 2 (100%) |
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
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May 15, 2008 - 2:59 PM
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 Enthusiast Joined Feb 7, '07 From Portland, Oregon Currently Offline Reputation: 67 (96%) |
ugh.
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May 15, 2008 - 4:14 PM
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 Enthusiast Joined Jul 26, '07 From riverside,CA Currently Offline Reputation: 0 (0%) |
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. |
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May 15, 2008 - 4:37 PM
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 Enthusiast Joined Mar 19, '07 From Washington Currently Offline Reputation: 9 (100%) |
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. |
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May 15, 2008 - 4:45 PM
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 Enthusiast Joined Oct 7, '06 From wyomissing pennsylvania Currently Offline Reputation: 2 (100%) |
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 |
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May 15, 2008 - 4:51 PM
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Enthusiast Joined Nov 1, '07 From Santa Barbara, CA Currently Offline Reputation: 2 (100%) |
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  .
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May 15, 2008 - 8:16 PM
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Enthusiast Joined Apr 2, '07 From Great Western Plateau Currently Offline Reputation: 9 (100%) |
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 |
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May 15, 2008 - 10:01 PM
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Enthusiast Joined Aug 29, '02 From Lake Orion, MI Currently Offline Reputation: 6 (100%) |
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....
-------------------- -Mike
mjcoury@gmail.com Team Reynolds Style Celica Blog Celica Wiki It 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. |
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May 15, 2008 - 10:15 PM
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Enthusiast Joined Nov 1, '07 From Santa Barbara, CA Currently Offline Reputation: 2 (100%) |
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.  http://www.engr.ucsb.edu/~me151c/Hw5.pdf back to work |
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May 15, 2008 - 11:20 PM
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Enthusiast Joined Aug 29, '02 From Lake Orion, MI Currently Offline Reputation: 6 (100%) |
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. 
-------------------- -Mike
mjcoury@gmail.com Team Reynolds Style Celica Blog Celica Wiki It 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. |
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May 15, 2008 - 11:27 PM
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Enthusiast Joined Aug 29, '02 From Lake Orion, MI Currently Offline Reputation: 6 (100%) |
I dunno... maybe the integration by parts needs to be done from 0 -> inf as well?
not likely though... -------------------- -Mike
mjcoury@gmail.com Team Reynolds Style Celica Blog Celica Wiki It 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. |
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May 15, 2008 - 11:31 PM
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Enthusiast Joined Aug 29, '02 From Lake Orion, MI Currently Offline Reputation: 6 (100%) |
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. http://www.engr.ucsb.edu/~me151c/Hw5.pdf back to work <Shudders> this is why I am an EE <shudders> -------------------- -Mike
mjcoury@gmail.com Team Reynolds Style Celica Blog Celica Wiki It 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. |
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May 15, 2008 - 11:33 PM
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 Enthusiast Joined Aug 31, '02 From Philadelphia, PA Currently Offline Reputation: 8 (100%) |
The answer is C.
-------------------- 15PSI - 30MPG - Megasquirt Tuned
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May 16, 2008 - 7:41 AM
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Enthusiast Joined Aug 29, '02 From Lake Orion, MI Currently Offline Reputation: 6 (100%) |
@Lagos,
Where were you before I spent an hour on this? -------------------- -Mike
mjcoury@gmail.com Team Reynolds Style Celica Blog Celica Wiki It 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. |
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May 16, 2008 - 10:09 AM
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 Enthusiast Joined Dec 25, '02 From Pittsburgh/Clairton, PA Currently Offline Reputation: 1 (100%) |
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 --------------------  |
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May 16, 2008 - 10:25 AM
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Enthusiast Joined Dec 25, '02 From Pittsburgh/Clairton, PA Currently Offline Reputation: 1 (100%) |
just skimmed the 2nd search result till i saw Sin.
page 13 http://www.math.utah.edu/~gustafso/2250LaplaceTheory.pdf has your exact solutions, tsinat = 2sa/(s²+a²)² -------------------- |
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May 16, 2008 - 10:41 AM
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Enthusiast Joined Aug 29, '02 From Lake Orion, MI Currently Offline Reputation: 6 (100%) |
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 ****... -------------------- -Mike
mjcoury@gmail.com Team Reynolds Style Celica Blog Celica Wiki It 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. |
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May 16, 2008 - 10:58 AM
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Enthusiast Joined Apr 2, '07 From Great Western Plateau Currently Offline Reputation: 9 (100%) |
Ahhh I know what Im forgetting now...
 Cheers for all da help...now i know where to go when im stuck!
-------------------- 98% completion --- aaRon |
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May 16, 2008 - 11:20 AM
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Enthusiast Joined Dec 25, '02 From Pittsburgh/Clairton, PA Currently Offline Reputation: 1 (100%) |
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 
This post has been edited by Consynx: May 16, 2008 - 11:27 AM -------------------- |
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