For any two sets `A and B ,` prove that `AuuB=AnnBhArrA=B`

Explanation

To prove that for any two sets \( A \) and \( B \), \( A \cup B = A \cap B \) if and only if \( A = B \), we will follow these steps:

### Step 1: Assume \( A \cup B = A \cap B \)

We start by assuming that \( A \cup B = A \cap B \).

### Step 2: Show that \( A \subseteq B \)

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