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Trigonometry and Modelling

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Question 22

Let f(θ)=3cos⁡θ−6sin⁡θf(\theta) = 3\cos\theta - 6\sin\thetaf(θ)=3cosθ−6sinθ for θ∈R\theta \in \mathbb{R}θ∈R.

a.

Express f(θ)f(\theta)f(θ) in the form Rcos⁡(θ+α)R\cos(\theta + \alpha)Rcos(θ+α), where R>0R > 0R>0 and 0<α<π20 < \alpha < \frac{\pi}{2}0<α<2π​. Give the exact value of RRR and the value of α\alphaα, in radians, to 3 decimal places.

[3]
b.

The curve with equation y=cos⁡θy = \cos\thetay=cosθ is transformed onto the curve with equation y=f(θ)y = f(\theta)y=f(θ) by a sequence of two transformations.

Given that the first transformation is a stretch and the second is a translation:

(i) Describe fully the transformation that is a stretch. (ii) Describe fully the transformation that is a translation.

[4]
c.

Given g(θ)=755+(f(θ))2g(\theta) = \frac{75}{5 + (f(\theta))^2}g(θ)=5+(f(θ))275​, find the range of ggg.

[3]

Trigonometry and Modelling Questions

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