Q18 of 48 Page 86

If cos 2θ = sin 4θ are acute angles then find the value of θ.

As given 2θ and 4θ are acute angles.


⇒ cos 2θ = sin 4θ


⇒ sin (90˚ – 2θ) = sin 4θ


⇒ 90˚ – 2θ = 4θ


⇒ 6θ = 90˚


⇒ θ = = 15˚


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