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February 17th, 2017, 01:18 AM  #1 
Newbie Joined: Feb 2017 From: MHDIR Posts: 2 Thanks: 0  proving formula of Laplace
Hello everybody I want to find how to proving formula of Laplace in pic no1 from the basic limit formula of pic no.2 Thank and best regards 
February 17th, 2017, 02:42 AM  #2 
Senior Member Joined: Feb 2016 From: Australia Posts: 1,533 Thanks: 513 Math Focus: Yet to find out. 
All of them? Could you pick one that you're finding particularly difficult maybe? 
February 17th, 2017, 03:16 AM  #3 
Senior Member Joined: Feb 2016 From: Australia Posts: 1,533 Thanks: 513 Math Focus: Yet to find out. 
Start with an easy one i guess... Let $\displaystyle f(t) = u(t) = $$\displaystyle \left\{ \begin{array}{rl} 0, &\mbox{ t $\displaystyle <$ 0} \\ 1, &\mbox{ t $\displaystyle \geq$ 0} \end{array} \right. $ Since we aren't concerned values of $\displaystyle t$ less than $\displaystyle 0$, we can allow $\displaystyle f(t) = 1$. Then we simply need to compute the following, which ill leave you to do . $\displaystyle \int_{0}^{\infty} e^{s t} dt$ 
February 17th, 2017, 09:44 AM  #4  
Newbie Joined: Feb 2017 From: MHDIR Posts: 2 Thanks: 0  Quote:
because i passed this in three yrs ago in college, and i forgotten the details. best regards Last edited by almahdi; February 17th, 2017 at 10:29 AM.  
February 19th, 2017, 10:09 PM  #5 
Senior Member Joined: Feb 2016 From: Australia Posts: 1,533 Thanks: 513 Math Focus: Yet to find out.  Yes but what details exactly? Trouble with integration or applying the definition of L.T. ?

February 26th, 2017, 12:19 AM  #6 
Senior Member Joined: Feb 2016 From: Australia Posts: 1,533 Thanks: 513 Math Focus: Yet to find out. 
I wrote a few of them up. Let me know if there are any mistakes.


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formula, laplace, proving 
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