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Question
If cos 2θ = sin 4θ where 2θ, 4θ are acute angles, find the value of θ.
Solution
We know that sin (90 - θ) = cos θ
sin 20 = cos 2θ
sin 4θ = sin (90 - 2θ)
4θ = 90 – 20
6θ = 90
`θ = 90/6`
θ = 15°
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