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--- strings_and_languages [2012/09/19 16:55]
vkuncak
+++ strings_and_languages [2019/07/02 16:16] (current)
fabien [Strings and languages]
@@ Line 36: / Line 36: @@
 Observe that
-\[
+\begin{equation*}
    \emptyset \cdot L = \{ s_1 \cdot s_2 \mid s_1 \in \emptyset \land s_2 \in L \} = \{s_1 \cdot s_2 \mid \mbox{false} \} = \emptyset
-\]
+\end{equation*}
 Similarly, $L \cdot \emptyset = \emptyset$.
-Of course, $\{ w_1 \} \cdot \{ w_2 \} = w_1\cdot w_2$.
+Also directly from definition follows:
+\begin{equation*}
+  \{ w_1 \} \cdot \{ w_2 \} = \{ w_1\cdot w_2 \}
+\end{equation*}