Question

If cos 2θ = sin 4θ and 2θ is acute, then find the value of θ.

Answer 1

we have

cos2θ  = sin 4θ 

⇒ sin(90° - 2θ) = sin 4θ 

comparing both sides, we get

90° - 2° = 4θ

⇒ 2θ + 4θ = 90°

⇒ 6θ= 90°

⇒ θ = \(\frac{90^\circ}6\)

∴ θ = 15°

Hence, the value of θ is 15°