f(x)=sin^2ax-sinaxcosax
=(1-cos2ax)/2-(sin2ax)/2
=-(1/2)sin2ax-(1/2)cos2ax+1/2
=-(√2/2)[sin2ax*cos(π/4)+cos2ax*cos(π/4)]+1/2
=-(√2/2)sin(2ax+π/4)+1/2
（1）周期t=2π/(2a)=π/2
∴ a=2
（2）f(x)=-(√2/2)sin(4x+π/4)+1/2
单调减区间,即求y=sin(4x+π/4)的增区间
∴ 2kπ-π/2≤4x+π/4≤2kπ+π/2,k∈Z
∴ 2kπ-3π/4≤4x≤2kπ+π/4,k∈Z
∴ kπ/2-3π/16≤x≤kπ/2+π/16,k∈Z
即减区间是[kπ/2-3π/16,kπ/2+π/16],k∈Z f(x)=sin^2ax-sinaxcosax
=(1-cos2ax)/2-(sin2ax)/2
=-(1/2)sin2ax-(1/2)cos2ax+1/2
=-(√2/2)[sin2ax*cos(π/4)+cos2ax*cos(π/4)]+1/2
=-(√2/2)sin(2ax+π/4)+1/2
（1）周期t=2π/(2a)=π/2
∴ a=2
（2）f(x)=-(√2/2)sin(4x+π/4)+1/2
单调减区间,即求y=sin(4x+π/4)的增区间
∴ 2kπ-π/2≤4x+π/4≤2kπ+π/2,k∈Z
∴ 2kπ-3π/4≤4x≤2kπ+π/4,k∈Z
∴ kπ/2-3π/16≤x≤kπ/2+π/16,k∈Z
即减区间是[kπ/2-3π/16,kπ/2+π/16],k∈Z