November 13th, 2010, 05:45 AM  #1 
Member Joined: Jun 2010 Posts: 80 Thanks: 0  Integration and expansion
I have 2 problems, a) a function f(x,t) should be expanded in or is it sufficient as ? a) if I can write functions is it possible to write f1(t)f2(t) as integral of the previous function, like : , or double integral ? 
November 13th, 2010, 07:08 AM  #2 
Senior Member Joined: Oct 2010 From: Changchun, China Posts: 492 Thanks: 14  Re: Integration and expansion
a)I don't know what you want to do, orthogonal decomposition or something else? b)Obviously not. 
November 19th, 2010, 02:55 AM  #3 
Member Joined: Jun 2010 Posts: 80 Thanks: 0  Re: Integration and expansion
I made a lot of mistake inside, for (a) i meant how to write generally the basis of all the function u(x,t) ? 
November 19th, 2010, 12:41 PM  #4 
Newbie Joined: Nov 2010 Posts: 13 Thanks: 0  Re: Integration and expansion
Sorry, but I have a question. I can't post my problem; since I need to type some mathematical formula and I don't know how to such stuff . I want to insert integration symbol, subscript, superscript, ...etc. Thanks in advance.. 
November 19th, 2010, 03:02 PM  #5 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,155 Thanks: 461 Math Focus: Calculus/ODEs  Re: Integration and expansion
This forum allows the use of LaTex to format equations and symbols, etc. Check out this topic which has some useful links. 
November 20th, 2010, 03:15 PM  #6 
Member Joined: Jun 2010 Posts: 80 Thanks: 0  Re: Integration and expansion
Well we could see as a complete Fourier transformation in k,omega, but I don't know why, physically, a "timebasis" seems a bit "naive", in the sense the future always remains hidden ? 
November 21st, 2010, 03:53 PM  #7 
Senior Member Joined: Oct 2010 From: Changchun, China Posts: 492 Thanks: 14  Re: Integration and expansion
There will allways be some cost (loss of energy or power etc.) doing a), even the function can be decomposed by the Fourier transform.


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