Laplace Transform Practice: Finding Inverse and Basic Forms

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Homework Help Overview

The discussion revolves around finding the Laplace transforms of the functions t sin(t) and t cos(t), as well as the inverse transform of the expression \(\frac{1}{(1+s^2)^2}\). Participants are exploring the relationships between these transforms and how to apply them in the context of the problem.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the Laplace transforms they have found and express uncertainty about how to use them to find the inverse transform. There are hints about using convolution and references to known transforms, prompting further exploration of the relationships between the functions involved.

Discussion Status

The discussion is active, with participants providing hints and partial solutions. Some have suggested methods like convolution, while others are questioning the basic transforms of sine and cosine functions. There is no explicit consensus yet, but the dialogue is guiding towards potential approaches.

Contextual Notes

Participants reference a table of Laplace transforms for quick checks, indicating that they are working within the constraints of available resources and possibly time limitations related to homework or exam preparation.

leopard
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Homework Statement



Find the laplace transform of t sin(t) and t cos(t), and the inverse transform of [tex]\frac{1}{(1+s^2)^2}[/tex]

2. The attempt at a solution

I found the two laplace forms:

[tex]\frac{2s}{(s^2+1)^2}[/tex]

and

[tex]\frac{s^2-1}{(s^2+1)^2}[/tex]

I guess I'm supposed to use the two laplace transforms to find the inverse of this one, but I don't know how to do that.
 
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You can try convolution... doesn't look hard. I partially solved it.
 
Hint: what is the Laplace transform of [itex]\sin(t)[/itex]?
 
leopard said:

Homework Statement



Find the laplace transform of t sin(t) and t cos(t), and the inverse transform of [tex]\frac{1}{(1+s^2)^2}[/tex]

2. The attempt at a solution

I found the two laplace forms:

[tex]\frac{2s}{(s^2+1)^2}[/tex]

and

[tex]\frac{s^2-1}{(s^2+1)^2}[/tex]

I guess I'm supposed to use the two laplace transforms to find the inverse of this one, but I don't know how to do that.

This is the best table I found if you need a quick answer in your research or to check your answer: http://www.vibrationdata.com/Laplace.htm.

For example check out 2.18, 2.20, and 2.21
 
gabbagabbahey said:
Hint: what is the Laplace transform of [itex]\sin(t)[/itex]?

[tex]\frac{1}{s^2 + 1}[/tex]
 
leopard said:
[tex]\frac{1}{s^2 + 1}[/tex]

Right, and so what is [tex]\mathcal{L}[\sin(t)-t\cos(t)][/tex]?:wink:
 
Lol, it's so easy when you know the answer. One must be evil to give such a problem for the exam.
 

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