log2(sinxcosx)=log2(1/2sin2x)=log2(sin2x)-1
sin2x>0
2x∈(2kπ,2kπ+π)
x∈(kπ,kπ+π/2)
∵2>0
∴单调递增区间为x∈(kπ,kπ+π/4)