If `A sub U`, prove that :
(i) `U' =phi` (ii) ` phi' =U` (iii) `(A')' =A ` (iv) ` A cup A' =U ` (v) `A cap A' =phi`

Explanation

To prove the given statements about the set \( A \) which is a subset of the universal set \( U \), we will go through each part step by step.

### Given:
- \( A \subseteq U \) (A is a subset of U)
- \( U \) is the universal set.

### To Prove:
1. \( U' = \phi \)
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