Prove the following Closure Properties with respect to Context
Free Languages.
1. Show that Context Free Languages are Closed under union(∪),
concatenation(·), kleene star(*).
(Hint: If L1 and L2 are Context Free languages then write
Context Free grammar equivalent to L1 ∪ L2, L1 · L2, L∗ 1 )
2. Show that if L1 and L2 are Context Free Languages, then L1 ∩
L2 is not necessarily Context Free.
(Hint: Use Proof by Counter Example)