diff --git a/ws2020/ana/uebungen/ana3-bonus.pdf b/ws2020/ana/uebungen/ana3-bonus.pdf deleted file mode 100644 index bd51b88..0000000 Binary files a/ws2020/ana/uebungen/ana3-bonus.pdf and /dev/null differ diff --git a/ws2020/ana/uebungen/ana3-bonus.tex b/ws2020/ana/uebungen/ana3-bonus.tex deleted file mode 100644 index bca8611..0000000 --- a/ws2020/ana/uebungen/ana3-bonus.tex +++ /dev/null @@ -1,46 +0,0 @@ -\documentclass{../../../lecture} - -\usepackage[]{mathrsfs} - -\begin{document} - -\begin{aufgabe} - Beh.: $f$ genau dann messbar, wenn $f^{-1}(\mathscr{A}) \subset \mathscr{E}$. - \begin{proof} - ,,$\implies$'': trivial, denn $f$ messbar $\implies$ $f^{-1}(\mathscr{F}) \subset \mathscr{E}$ und da $\mathscr{A} \subset \mathscr{F}$, folgt - $f^{-1}(\mathscr{A}) \subset \mathscr{E}$. - - ,,$\impliedby$'': Sei also $f^{-1}(\mathscr{F}) \subset \mathscr{E}$. - Also $f^{-1}(\mathscr{F}) = \{ f^{-1}(A) \mid A \in \mathscr{F} \} \subset \mathscr{E}$. - \[ - \mathscr{K} := \{ A \in \mathscr{F} \mid f^{-1}(A) \in \mathscr{E}\} - .\] - - Z.z.: $\mathscr{K}$ $\sigma$-Algebra. - \begin{enumerate}[(i)] - \item $Y \in \mathscr{K}$, denn - $f^{-1}(Y) = X \in \mathscr{E}$, da $\mathscr{E}$ - $\sigma$-Algebra. - \item Sei $A \in \mathscr{A}$. Dann ist - $f^{-1}(A) \in \mathscr{E}$ und damit - $f^{-1}(A^{c}) = f^{-1}(A)^{c} \in \mathscr{E}$, da - $\mathscr{E}$ $\sigma$-Algebra. - \item Seien $A_i \in \mathscr{K}$ für $i \in \N$. Dann - ist $\forall i \in \N$: $f^{-1}(A_i) \in \mathscr{E}$. Damit - folgt, da $\mathscr{E}$ $\sigma$-Algebra: - \[ - f^{-1}\left(\bigcup_{i \in \N} A_i \right) - = \bigcup_{i \in \N} f^{-1}(A_i) \in \mathscr{E} - .\] - \end{enumerate} - Nach Voraussetzung ist $\mathscr{A} \subset \mathscr{K}$. Es - ist $\mathscr{K} \subset \mathscr{F}$ und - $\mathscr{K}$ $\sigma$-Algebra, die $\mathscr{A}$ enthält, damit - folgt $\mathscr{F} = \sigma(\mathscr{A}) \subset \mathscr{K}$, - also insgesamt $\mathscr{K} = \mathscr{F}$. Also - folgt $\forall A \in \mathscr{F}\colon f^{-1}(A) \in \mathscr{E}$, also - $f^{-1}(\mathscr{F}) \subset \mathscr{E}$. - \end{proof} -\end{aufgabe} - -\end{document}