Kapitel 2 fortgesetzt
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.gitignore
vendored
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5
.gitignore
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.DS_Store
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*.aux
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*.log
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*.synctex.gz
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*.toc
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72
I_2.tex
72
I_2.tex
@@ -112,63 +112,61 @@ Zur Vorbereitung dieser wichtigen Beweismethode werden zunächst einige Begriffe
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\input{Definitionen/I_D_21.tex}
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%%%%%%%%BIN HIER %%%%%%%%%%%%%%%%
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-16-
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\newpage
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-17-
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Beispiel 15
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2.3
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Das Summenzeichen dient also dazu, endliche Summen von Ausdrücken oder Termen effizient und platzsparend darzustellen.
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Beispiel 16
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a) $1+2+3+\ldots+n-1+n=\sum_{k=1}^{n} k$
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-17-
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\begin{beispiel}\label{B0016}
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\begin{enumerate}[a)]
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\item $1+2+3+\ldots+n-1+n=\sum_{k=1}^{n} k$
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\item $2^{3}+2^{2}+2+1+\frac{1}{2}+\frac{1}{2^{2}}+\frac{1}{2^{3}}+\ldots+\frac{1}{2^{50}}=\sum_{k=-3}^{50} \frac{1}{2^{k}}$
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\item $\sqrt{\left(x-x_{1}\right)^{2}+\left(x-x_{2}\right)^{2}+\left(x-x_{3}\right)^{2}+\ldots+\left(x-x_{l}\right)^{2}}=\sqrt{\sum_{k=1}^{l}\left(x-x_{k}\right)^{2}}$
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\end{enumerate}
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\end{beispiel}
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\newpage
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-18-
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b) $2^{3}+2^{2}+2+1+\frac{1}{2}+\frac{1}{2^{2}}+\frac{1}{2^{3}}+\ldots+\frac{1}{2^{50}}=\sum_{k=-3}^{50} \frac{1}{2^{k}}$
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c) $\sqrt{\left(x-x_{1}\right)^{2}+\left(x-x_{2}\right)^{2}+\left(x-x_{3}\right)^{2}+\ldots+\left(x-x_{l}\right)^{2}}=\sqrt{\sum_{k=1}^{l}\left(x-x_{k}\right)^{2}}$
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Für das Rechnen mit dem Summenzeichen gelten die im folgenden Satz zusammengestellten Gesetze.
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\begin{satz}\label{S0001}
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\begin{align}
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\sum_{k=m}^{n} a_{k}+\sum_{k=m}^{n} b_{k} &=\sum_{k=m}^{n}\left(a_{k}+b_{k}\right) \\
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\sum_{k=m}^{n} c \cdot a_{k} &=c \sum_{k=m}^{n} a_{k} \\
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\sum_{k=m}^{n} a_{k} &=\sum_{i=m}^{n} a_{i}=\sum_{j=m}^{n} a_{j} \\
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\sum_{k=m}^{n} a_{k} &=\sum_{k=m}^{u} a_{k}+\sum_{k=u+1}^{n} a_{k} \quad \text { für } m \leq u \leq n \\
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\sum_{k=m}^{n} a_{k} \sum_{i=u}^{v} b_{i} &=\sum_{k=m}^{n} \sum_{i=u}^{v} a_{k} b_{i}=\sum_{i=u}^{v} \sum_{k=m}^{n} a_{k} b_{i}
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\end{align}
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Für eine beliebige Zahl $l \in \mathbb{Z}$ lässt sich eine \textbf{Indexverschiebung} im Summenzeichen vornehmen. Es gilt:
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\begin{align}
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\sum_{k=m}^{n} a_{k}+\sum_{k=m}^{n} b_{k} &=\sum_{k=m}^{n}\left(a_{k}+b_{k}\right) \\
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\sum_{k=m}^{n} c \cdot a_{k} &=c \sum_{k=m}^{n} a_{k} \\
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\sum_{k=m}^{n} a_{k} &=\sum_{i=m}^{n} a_{i}=\sum_{j=m}^{n} a_{j} \\
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\sum_{k=m}^{n} a_{k} &=\sum_{k=m}^{u} a_{k}+\sum_{k=u+1}^{n} a_{k} \quad \text { für } m \leq u \leq n \\
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\sum_{k=m}^{n} a_{k} \sum_{i=u}^{v} b_{i} &=\sum_{k=m}^{n} \sum_{i=u}^{v} a_{k} b_{i}=\sum_{i=u}^{v} \sum_{k=m}^{n} a_{k} b_{i}
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\end{align}
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Für eine beliebige Zahl $l \in \mathbb{Z}$ lässt sich eine \textbf{Indexverschiebung} im Summenzeichen vornehmen. Es gilt:
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\begin{align}
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\sum_{k=m}^{n} a_{k}=\sum_{k=m+l}^{n+1} a_{k-l}
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\sum_{k=m}^{n} a_{k}=\sum_{k=m+l}^{n+1} a_{k-l}
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\end{align}
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\end{satz}
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Beweis:
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Mit der Definition $2.1$ gilt :
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(1) $\sum_{k=m}^{n} a_{k}+\sum_{k=m}^{n} b_{k}=a_{m}+a_{m+1}+\ldots+a_{n}+b_{m}+b_{m+1}+\ldots+b_{n}$
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%%%%%%%%BIN HIER %%%%%%%%%%%%%%%%
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\newpage
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\newpage
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\textbf{Beweis}:
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Mit der Definition \ref{D1_1_21} gilt :
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\begin{enumerate}[(1)]
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\item $\sum_{k=m}^{n} a_{k}+\sum_{k=m}^{n} b_{k}=a_{m}+a_{m+1}+\ldots+a_{n}+b_{m}+b_{m+1}+\ldots+b_{n}$
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$$
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=a_{m}+b_{m}+a_{m+1}+b_{m+1}+\ldots+a_{n}+b_{n}=\sum_{k=m}^{n}\left(a_{k}+b_{k}\right)
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$$
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(2) $\sum_{k=m}^{n} c \cdot a_{k}=c \cdot a_{m}+c \cdot a_{m+1}+\ldots+c \cdot a_{n}$
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\item $\sum_{k=m}^{n} c \cdot a_{k}=c \cdot a_{m}+c \cdot a_{m+1}+\ldots+c \cdot a_{n}$
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$$
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=c \cdot\left(a_{m}+a_{m+1}+\ldots+a_{n}\right)=c \sum_{k=m}^{n} a_{k}
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$$
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\end{enumerate}
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-18-
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\newpage
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@@ -25,13 +25,13 @@
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#text(2em, weight: "bold")[Band I - Mengen]
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]
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#v(2em)
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#include("Definitionen.typ")
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//#include("Definitionen.typ")
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= Vorwort
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#include("I_Vorwort.typ")
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= Grundzüge der Mengenlehre
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//#include("I_1.typ")
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#include("I_1.typ")
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/* \input */
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/*= Mathematische Beweismethoden
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/* \input */I_(2).tex
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