Giải phương trình lượng giác: 1) sin(2x - pi/6).cosx = 0; 2) tan^2(3x - 3pi/4) = 3

1. sin(2x - pi/6).cosx = 0
2. tan^2(3x - 3pi/4) = 3
3. sin3x.cos2x+sinx = 0
4. cos2x.cos5x = cos3x.cos4x
5. sin^25x - cos^2(7pi/4 - x) = 0
6. cos2x.cosx - cosx.cos3x = sin2x.sinx - sin3x.sinx