Set Identities Cbe4B9
1. **State the problem:** Prove the identities using algebraic laws of sets:
(i) $ (A \cup B) \cap (A \cup B^c) = A $
(ii) $ A \cup (A \cap B) = A $
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2. **Recall important laws:**
- Distributive law: $X \cap (Y \cup Z) = (X \cap Y) \cup (X \cap Z)$ and vice versa.
- Complement law: $B \cup B^c = U$ (universal set).
- Idempotent law: $A \cup A = A$ and $A \cap A = A$.
- Absorption law: $A \cup (A \cap B) = A$.
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3. **Proof of (i):**
Start with the left side:
$$ (A \cup B) \cap (A \cup B^c) $$
Use distributive law:
$$ = A \cup (B \cap A) \cup (B \cap B^c) $$
Note $B \cap A = A \cap B$ and $B \cap B^c = \emptyset$ (empty set), so:
$$ = A \cup (A \cap B) \cup \emptyset = A \cup (A \cap B) $$
By absorption law:
$$ = A $$
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4. **Proof of (ii):**
By absorption law directly:
$$ A \cup (A \cap B) = A $$
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**Final answers:**
(i) $ (A \cup B) \cap (A \cup B^c) = A $
(ii) $ A \cup (A \cap B) = A $