Q. 12 B5.0( 3 Votes )

Find θ if cos(2 θ +54o)= sin θ, where (2θ +54o) is an acute angle.

Answer :

cos(2 θ +54o)= sin θ …(i)

We know that

Sin θ = cos (90° - θ)

So, Eq. (i) become

cos(2 θ +54o) = cos( 90° - θ)

On Equating both the sides, we get

2θ + 54° = 90° - θ

2θ + θ = 90° - 54°

3θ = 36°

θ = 12°

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