If \frac{\cos(\alpha -3\theta)}{\cos^3 \theta}=\frac{\sin(\alpha -3\theta)}{\sin^3 \theta}=m prove that \cos\alpha=\frac{2-m^2}{m}

Terrence Moore

Terrence Moore

Answered question

2022-04-22

If cos(α3θ)cos3θ=sin(α3θ)sin3θ=m prove that cosα=2m2m

Answer & Explanation

hadnya1qd

hadnya1qd

Beginner2022-04-23Added 15 answers

sinαsin3θ+cosαcos3θmcos3θ=0
sinαcos3θcosαsin3θmsin3θ=0
sinαm(cos3θsin3θ+cos3θsin3θ)=cosαm(cos3θcos3θsin3θsin3θ)=1
Using sin3θ, cos3θ formula
4sinαm=(cos3θ+3cosθ)sin3θ+cos3θ(3sinθsin3θ)=3sin(3θ+θ)
Similarly, 4cosαm=(cos3θ+3cosθ)cos3θsin3θ(3sinθsin3θ)=13cos(3θ+θ)
Use cos24θ+sin24θ=1

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