căn bậc 2 (3).sin2x.(2cosx+1)+2 = cos3x + cos2x - 3cosx
------------------------->
\[\sqrt{3} \sin 2x.(2\cos x + 1) + 2 = \cos 3x + \cos 2x - 3\cos x\\]
căn bậc 2 (3).sin2x.(2cosx+1)+2 = cos3x + cos2x - 3cosx
------------------------->
\[\sqrt{3} \sin 2x.(2\cos x + 1) + 2 = \cos 3x + \cos 2x - 3\cos x\\]