DIFFEQ - Discontinuous Forcing Functions (should be an easy question)

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SUMMARY

The discussion focuses on the application of Laplace transforms to a piecewise function defined as f(t) = u_1(t)(t^2 - 2t + 2). The user initially struggles with the correct application of the Laplace transform formula, specifically the use of the discontinuous forcing function. After some deliberation, the user realizes that rewriting the function allows for the correct application of the Laplace transform rules. The final expression derived is F(s) = e^{-cs}/s [L(t^2) + L(-2t) + L(2)], confirming the user's understanding of the topic.

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Ok, we just started this chapter, and I am slightly confused with one specific aspect of the info... I'll just go through an example, it's the best way to explain it IMHO.
I have to find the Laplace transform of the following function.
The table of transforms that I can use are (sorry about the formatting, I know they are not equal to each other):
[tex]u_c(t) = \frac{e^{-cs}}{s}[/tex]
[tex]u_c(t)f(t-c) = e^{-cs}F(s)[/tex]
[tex]t^n = \frac{n!}{s^{n+1}}[/tex]

[tex]f(t)=[/tex] is defined as a system of equations (sorry I don't know the LaTeX formatting for it).
[tex]f(t)=0|t<1[/tex]
[tex]f(t)=t^2-2t+2|t\geq1[/tex]

So [tex]f(t)[/tex] can be rewritten as:
[tex]f(t) = u_1(t)(t^2-2t+2)[/tex]

Ok, so now this is where I get confused. I have to do the Laplace transform of [tex]f(t) = u_1(t)(t^2-2t+2[/tex]. But the only table value I have is:
[tex]u_c(t)f(t-c) = e^{-cs}F(s)[/tex]

But, this doesn't actually match what I have. Since, f(t) is not of the form f(t-c). So if anyone could just explain this part better to me... that would be awesome. My thought process here is that I have to change f(t-c) to be f(t).
So:
[tex](t-1)^2 = t^2-2t+1[/tex]
[tex](t-1)^2 +1 = f(t)[/tex]
This would allow me to use the rule right?

So I would then have:

[tex]F(s) = e^{-cs}/s L((t-1)^2+1) = e^{-cs}/s [L(t^2)+L(-2t)+L(2)][/tex]

Is this idea even right? I guess I just don't understand what is really going on here.
On a second note what the hell is going on with the latex formatting? Is anyone else having troubles previewing their changes?
 
Last edited:
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Nevermind

Nevermind... I figured it out. Thanks though :)
If anyone wants to elaborate, be my guest.
 

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