# A question about fourier analysis

1. Aug 16, 2011

### rar0308

Hi.
see the image.
In the integral there's no dx,dy,dz thing. Does this make any sense?
Isn't it errata?

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Last edited: Aug 16, 2011
2. Aug 17, 2011

### mathfeel

It is wrong without the dx, dy, dz thing. If this comes from some hand written note, it's usually implied. If this comes from a book, you need to kick the editor in the nut...

3. Aug 17, 2011

### rar0308

Thanks.
It's from page 11 <Quantum Theory> David Bohm, Dover.

4. Aug 17, 2011

### daveyp225

It makes sense if the order does not matter for integration. If it is obvious in context that the variables here are x,y,z (L is clearly a constant as integrals contain it) and Fubini's Theorem is satisfied then you are free to choose.

5. Aug 18, 2011

### pwsnafu

How do you know that l, m, n, l', m', n' are constant?

6. Aug 18, 2011

### daveyp225

I said "if it was obvious in context the variables are x, y and z". Otherwise, call it a good hunch, as there are only three integration variables present and the ' notation often signifies a relationship between, for example, m and m'. All six cannot be integration variables, and if the first three were then the second sine function is only a constant with respect to integration and would probably not be part of the integrand.