text: sin2x - 2cosx = sinx - 1\n2sinxcosx - 2cosx = sinx - 1\n2cosx(sinx - 1) - (sinx - 1) = 0\n(sinx - 1)(2cosx - 1) = 0\nsinx = 1 or cosx = ½\nSo x = π/2, 3π/2 or x = π/3, 5π/3 (for 0 ≤ x ≤ 2π)\nie x = π/3, π/2, 3π/2 , 5π/3 (for 0 ≤ x ≤ 2π)