y = xcos（2x + π/2）sin（2x + π/2） y=1/2 Xsin(4x+π） =-1/2Xsin(4x） y'=-1/2(sin(4x)+4xcos(4x))
y'=cos(2x + π/2）sin（2x + π/2）-2x[sin（2x + π/2)^2+2x[cos(2x + π/2）]^2 =sin（4x + π）/2+2xcos(4x +π) =-(sin4x )/2-2xcos4x
