[TI] Compact: Add some notes

semester3/ti-compact/parts/01_words-alphabets.tex

@@ -31,10 +31,16 @@ whereas $L_\lambda$ is the language with just the empty word in it.
 
 \bi{Cleen Star}: $L^* = \bigcup_{i \in \N} L^i$ and $L^+ = L \cdot L^*$
 
+Of note is that there are irregular languages whose Cleen Star is regular, most notably,
+the language $L = \{ w \in \{ 0 \}^* \divides |w| \text{ is prime} \}$'s Cleen Star is regular,
+due to the fact that the prime factorization is regular
+
 
 \inlinelemma $L_1L_2 \cup L_1 L_2 = L_1(L_2 \cup L_3)$
 \inlinelemma $L_1(K_2 \cap L_3) \subseteq L_1 L_2 \cap L_1 L_3$
 
+For multiple choice questions, really think of how the sets would look to determine if they fulfill a requirement.
+
 
 \stepcounter{subsection}
 \subsection{Kolmogorov-Complexity}