Hi, I usually dont have any problems with Fubini's theorem, but there is something I just cant figure out. Let f be integrable, and a some positive constant. How do i apply the theorem to this integral:(adsbygoogle = window.adsbygoogle || []).push({});

[tex] \int_0^a\int_x^a \frac{1}{t}|f(t)|dtdx [/tex]

Really; I know the answer is

[tex]\int_0^a \int_0^t \frac{1}{t}|f(t)|dxdt[/tex]

but I just dont get it. To me this is not obvious (should it be?). Can someone explain this to me?

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# The use of Fubini's theorem

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