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Trigonometry and Modelling

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Question 75
a.

Express 8sin⁡x−15cos⁡x8 \sin x - 15 \cos x8sinx−15cosx in the form Rsin⁡(x−α)R \sin(x - \alpha)Rsin(x−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 function ggg is defined by

g(θ)=15+8sin⁡(3θ−π4)−15cos⁡(3θ−π4),θ>0 g(\theta) = 15 + 8 \sin\left(3\theta - \frac{\pi}{4}\right) - 15 \cos\left(3\theta - \frac{\pi}{4}\right), \quad \theta > 0 g(θ)=15+8sin(3θ−4π​)−15cos(3θ−4π​),θ>0

Find (i) the minimum value of g(θ)g(\theta)g(θ) (ii) the smallest value of θ\thetaθ at which this minimum value occurs.

[3]
c.

The function hhh is defined by

h(β)=5−(8sin⁡β−15cos⁡β)2 h(\beta) = 5 - (8 \sin \beta - 15 \cos \beta)^2 h(β)=5−(8sinβ−15cosβ)2

Find the range of hhh.

[4]

Trigonometry and Modelling Questions

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