This commit is contained in:
2020-05-21 10:18:59 +02:00
4 changed files with 15 additions and 11 deletions
BIN
View File
Binary file not shown.
+4 -7
View File
@@ -15,20 +15,17 @@
\begin{proof}
Sei $x \in \mathbb{K}^{n}$. Dann ist
\begin{salign}
\begin{salign*}
\Vert (\mathbb{I} + B) x \Vert
&= \Vert x + B x\Vert \\
&\stackrel{\text{Dreiecksungl.}}{\ge } \Vert x \Vert - \Vert Bx \Vert \\
&\stackrel{\Vert Bx \Vert \le \Vert B \Vert \Vert x \Vert}{\ge }
\Vert x \Vert - \Vert B \Vert \cdot \Vert x \Vert \\
&= ( \underbrace{1 - \Vert B \Vert}_{> 0}) \Vert x \Vert
.\end{salign}
Also hat die Gleichung $(\mathbb{I} + B) x = 0$ nur die Lösung $x = 0$, also
\intertext{Also hat die Gleichung $(\mathbb{I} + B) x = 0$ nur die Lösung $x = 0$, also
ist $(\mathbb{I} + B)$ injektiv und mit \ref{lemma:linabb} regulär.
Bleibt zu zeigen: $\Vert (\mathbb{I} + B)^{-1} \Vert \le \frac{1}{1 - \Vert B \Vert}$.
Es gilt
\begin{salign}
Es gilt}
1 &= \Vert \mathbb{I}\Vert \\
&= \Vert (\mathbb{I} + B) (\mathbb{I} + B)^{-1} \Vert \\
&= \Vert (\mathbb{I} + B)^{-1} + B (\mathbb{I} + B)^{-1} \Vert \\
@@ -36,7 +33,7 @@
- \Vert B (\mathbb{I} + B)^{-1} \Vert \\
&\ge \Vert (\mathbb{I} + B)^{-1} \Vert - \Vert B \Vert \cdot \Vert (\mathbb{I} + B)^{-1} \Vert \\
&= (1 - \Vert B \Vert) \Vert (\mathbb{I} + B)^{-1} \Vert
.\end{salign}
.\end{salign*}
Damit folgt die Behauptung.
\end{proof}
BIN
View File
Binary file not shown.
+9 -2
View File
@@ -162,10 +162,17 @@
% uses regular expressions to calculate the widest stackrel
% to put additional padding on both sides of relation symbols
\NewEnviron{salign}
{
\begin{align}
\lec_insert_padding:V \BODY
\end{align}
}
% starred version that does no equation numbering
\NewEnviron{salign*}
{
\begin{align*}
\lec_insert_padding:V \BODY
.\end{align*}
\end{align*}
}
% some helper variables
@@ -210,7 +217,7 @@
}
% replace all relations with align characters (&) and add the needed padding
\regex_replace_all:nnN
{ (&=|&\c{le}|&\c{ge}|&\c{stackrel}{.*?}{.*?}|&\c{neq}) }
{ (\c{approx}&|&\c{approx}|\c{equiv}&|&\c{equiv}|=&|&=|\c{le}&|&\c{le}|\c{ge}&|&\c{ge}|&\c{stackrel}{.*?}{.*?}|\c{stackrel}{.*?}{.*?}&|&\c{neq}|\c{neq}&) }
{ \c{kern} \u{l_tmp_dim_needed} \1 \c{kern} \u{l_tmp_dim_needed} }
\l__lec_text_tl
\l__lec_text_tl