The correct option is B 2cos x
sin7x+6sin5x+17sin3x+12sin xsin6x+5sin4x+12sin2x=(sin7x+sin5x)+5(sin5x+sin3x)+12(sin3x+sinx)sin6x+5sin4x+12sin2x=2sin6xcosx+10sin4xcosx+12sin2xcosxsin6x+5sin4x+12sin2x=2cosx(sin6x+5sin4x+12sin2x)sin6x+5sin4x+12sin2x=2cosx