sin5x+2sin6x+sin7x=2sin6xcosx+2sin6x=2sin6x(cosx+1)
2cosx+cos2x+cos4x=2cosx+2cos3xcosx=2cosx(1+cos3x)
sin5x+2sin6x+sin7x=2sin6xcosx+2sin6x=2sin6x(cosx+1)
2cosx+cos2x+cos4x=2cosx+2cos3xcosx=2cosx(1+cos3x)