∵y=cos2(x+
)-cos2(x-π 4
)π 4
=
-1+cos(2x+
)π 2 2
1+cos(2x-
)π 2 2
=
-1-sin2x 2
1+sin2x 2
=-sin2x.
∴T=
=π.2π 2
又函数f(x)=-sin2x的定义域为R,
且f(-x)=-sin(-2x)=sin2x=-(-sin2x)=-f(x).
∴函数y=cos2(x+
)-cos2(x-π 4
)是最小正周期为π的奇函数.π 4
故选:D.