The equation cos² θ =(x + y)²is only possible

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The equation cos² θ = (x + y)² is only possible when
4xy

1. x = – y
2. x > y
3. x = y
4. x < y

Correct Option: C

cos² θ ≤ 1

∴	(x + y)²	≤ 1
	4 xy

⇒ (x + y) ² – 4xy ≤ 0
⇒ (x – y)² ≥ 0
⇒ x = y