y=2sinx(sinx-cosx)=2(sinx)^2-2sinxcosx
=1+cos2x-sin2x
=1+√2cos(2x+π/4)
求y的最大值1+√2此时cos(2x+π/4)=1
2x+π/4=2kπ
x=kπ-π/8
自变量x的集合{x|x=kπ-π/8,k∈Z}
单调递减区间2kπ
y=2sinx(sinx-cosx)=2(sinx)^2-2sinxcosx
=1+cos2x-sin2x
=1+√2cos(2x+π/4)
求y的最大值1+√2此时cos(2x+π/4)=1
2x+π/4=2kπ
x=kπ-π/8
自变量x的集合{x|x=kπ-π/8,k∈Z}
单调递减区间2kπ