cos4x+cos3x+cos2xsin4x+sin3x+sin2x=cos3x+2cos3xcosxsin3x+2sin3xcosx
=cos3x(1+2cosx)sin3x(1+2cosx)
=cot3x
Prove the following: cos 4x+ cos 3x + cos 2xsin 4x + sin 3x + sin 2x=cot 3x