Cos²θ -Sin²θ =1/3 then Cos⁴θ -Sin⁴θ =?

A 3

B 2

C 1

D 1/3

Correct Answer: Option D

Cos²θ -Sin²θ =1/3
এখন,
Cos⁴θ -Sin⁴θ
=(Cos²θ)²-(Sin²θ)²
=(Cos²θ+Sin²θ)(Cos²θ-Sin²θ)
=1×1/3
=1/3