[tex] \frac {d} {dt} \int_{a}^{b} f(x,t) dx = \int_{a}^{b} \frac {\delta} {\delta t} f(x,t) dx [/tex](adsbygoogle = window.adsbygoogle || []).push({});

From trial and error, it seems true but I can't find it in my textbook anywhere. Am I missing something obvious?

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# Is there a theorem that says

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