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Simple
Simple
05:30
Suppose $(X, \mathcal{S})$ is a measurable space. A function $f : X \to R$ is called
$\mathcal{S}$-measurable if $f^{-1}(B)\in\mathcal{S}$ for every Borel set $B\in\,R$.
if $f^{-1}(B)$ is a Borel set, then we call it Borel measure. Why does inverse images require in measurable space?

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