函数y=sin（π/4-2x）的单调递减区间是

函数y=sin（π/4-2x）的单调递减区间是

首先求导,y的导数=-2COS(π/4-2x).令导数小于0,则为递减区间.
即求-2COS(π/4-2x)小于0,则COS(π/4-2x)大于0.
2kπ-π/2<=π/4-2x<=2kπ+π/2
2kπ+π/2<=-2x<=2kπ+π/4
kπ-π/8<=x<=kπ-π/4

y=sin(Pai/4-2x)=-sin(2x-Pai/4)
函数y=sin（π/4-2x）的单调递减区间就是函数y=-sin(2x-Pai/4)的递增区间.
即2kPai-Pai/2<=2x-Pai/4<=2kPai+Pai/2
得:kPai-Pai/8<=x<=kPai+3Pai/8
即【kPai-Pai/8,kPai+3Pai/8】