Maths唔識抵死題(QUICK)

1. Solve the following equations for 0° < x < 360°

a)
Identity: sin(A - B) = sinA cosB - cosA sinB

sin3x cosx - cos3x sinx = (√3)/2
sin(3x - x) = (√3)/2
sin2x = (√3)/2
2x = 60°, 180° - 60°, 360° + 60°, 360° + 180° - 60°
2x = 60°, 120°, 420°, 480°
x = 30°, 60°, 210°, 240°


b)
4sin²x + 5 sinx cosx = 4
4sin²x + 5 sinx cosx = 4(sin²x + cos²x)
5sinx cosx - 4cos²x = 0
cosx(5sinx - 4cosx) = 0
cosx = 0 or 5sinx = 4cosx
cosx = 0 or sinx/cosx = 4/5
cosx = 0 or tanx = 0.8
x = 90°, 360° - 90° or x = 38.66°, 180° + 38.66°
x = 90°, 270°, 38.66°, 218.66°

the ans is wrong, the first one is 60, 210 and 240 and the second one is 90, 270, 23.6, 156.4