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1 Pure Mathematics

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Question 287

You may use the identity sin⁡3x≡3sin⁡x−4sin⁡3x\sin 3x \equiv 3\sin x - 4\sin^3 xsin3x≡3sinx−4sin3x.

a.

Solve, for 0≤x<π0 \leq x < \pi0≤x<π, the equation

8sin⁡3x−6sin⁡x+1=08\sin^3 x - 6\sin x + 1 = 08sin3x−6sinx+1=0

Give your answers in terms of π\piπ.

[4]
b.

Hence write down the four solutions, in the interval 0≤y<π2\displaystyle 0 \leq y < \frac{\pi}{2}0≤y<2π​, of the equation

8sin⁡32y−6sin⁡2y+1=08\sin^3 2y - 6\sin 2y + 1 = 08sin32y−6sin2y+1=0

[3]
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