If cos²θ – sin²θ = (1 / 3) , where

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If cos²θ – sin²θ = (1 / 3) , where 0 ≤ q ≤ (π / 2) , then the value of cos⁴θ – sin⁴θ is

1. 1
  3
2. 2
  3
3. 1
  9
4. 2
  9

Correct Option: A

cos² θ - sin² θ =	1
	3

cos⁴ θ – sin⁴ θ
= (cos² θ + sin² θ) (cos² θ – sin² θ)

= 1 ×		1	=	1
		3		3