You may use the identity sin3x≡3sinx−4sin3x\sin 3x \equiv 3\sin x - 4\sin^3 xsin3x≡3sinx−4sin3x.
Solve, for 0≤x<π0 \leq x < \pi0≤x<π, the equation
8sin3x−6sinx+1=08\sin^3 x - 6\sin x + 1 = 08sin3x−6sinx+1=0
Give your answers in terms of π\piπ.
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
8sin32y−6sin2y+1=08\sin^3 2y - 6\sin 2y + 1 = 08sin32y−6sin2y+1=0