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00 Inbox/29593975 - Regular Expressions.md

@@ -28,4 +28,6 @@ A _regular expression_ $r$ over an alphabet $Sigma$ is defined recursively:
 > [!EXAMPLE]
 > The language $L$ over $Sigma = {a, b}$ containing the substring $a b$ is regular, since it can be expressed using the regular expression
 > $r = (a +b)^* a b (a + b)^*$
-	
+
+## Equivalence of regular expressions
+Two regular expressiosn $r$ and $s$ are _equivalent_ ($r eq.triple s$ or $r hat(eq) s$) if thy generate the same language ($L(r) eq L(s)$).