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2 variable delta function integration 
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#1
Aug1907, 09:12 PM

P: 3

1. The problem statement, all variables and given/known data
[tex]\int^{A}_{A}[/tex][tex]\int^{Bx}_{Bx}c\delta(xcos\varphi+ysin\varphid)dydx[/tex] where A, B, c, d are constant 2. Relevant equations 3. The attempt at a solution I have tried a few different ways to integrate this, but am completely confused with what happens to this kind of delta function when you integrate it. I know integrating a delta function usually gives you 1 but I don't think this can work in this case. The answer has A,B,c and d in it, so the limits must be used somewhere. This is one step in a much longer problem, but it is frustrating to get close to the end and get stuck because I can't find anything anywhere about delta functions of 2 variables. Some help would really be appreciated. 


#2
Sep1611, 03:35 AM

P: 4

Did you or anyone else figure out how to deal with this? I have the same problem.



#3
Sep1611, 07:58 AM

HW Helper
P: 1,391

One could, for example, use the following property of a delta function:
[tex]\delta(af(x)) = \frac{1}{a}\delta(f(x))[/tex] to factor out the cosine in the argument of the delta function and then perform the x integration. The x integration is then easy, but there's a trick  you don't know for sure if the delta function argument is zero inside the limits of x integration, so you'll have to think carefully about that. 


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