=（cos^2 x）' cos2x cosx^2 cos^3 x +cos^2 x (cos2x)' cosx^2 cos^3 x+ cos^2 x cos2x( cosx^2 )'cos^3 x +cos^2 x cos2x cosx^2 (cos^3 x )'
=-2cosxsinxcos2x cosx^2 cos^3 x-2sin2xcos^2 x cosx^2 cos^3 x -2xsinx^2cos^2 x cos2x cos^3 x -3sinxcos^2xcos^2 x cos2x cosx^2
=-2sinxcosx(cos2x-cosx)cosx^2 cos^3 x-(cos^2 x cos2x cos^2 x)(2xsinx^2cosx-3sinxcos^2)
=-sin2x(cos2x-cosx)cosx^2 cos^3 x-(cos^2 x cos2x cos^2 x)(2xsinx^2cosx-3sinxcos^2)