答：
y=sin2x+2sinxcosx+2cos2x
=2sin2x+2cos2x
=2√2sin(2x+π/4)
1）当sin(2x+π/4)=-1时,y的最小值为-2√2
2x+π/4=2kπ-π/2,x=kπ-3π/8,k∈Z
2）单调减区间满足：2kπ+π/2