f‘(x)=(cosx-sinx)sinx+(sinx+cosx)cosx
= sinxcosx-sin²x+sinxcosx+cos²x
=2sinxcosx+cos²x-sin²x
=sin2x+cos2x
=√2sin(2x+π/4)
单调区间啊
f‘(x)>0
即sin(2x+π/4)>0
则2x+π/4∈[2kπ,2kπ+π]
解得x∈[kπ-π/8,kπ+3π/8]k∈Z
这个是单调递增
单调递减是x∈[kπ+3π/8,kπ+7π/8]k∈Z
f‘(x)=(cosx-sinx)sinx+(sinx+cosx)cosx
= sinxcosx-sin²x+sinxcosx+cos²x
=2sinxcosx+cos²x-sin²x
=sin2x+cos2x
=√2sin(2x+π/4)
单调区间啊
f‘(x)>0
即sin(2x+π/4)>0
则2x+π/4∈[2kπ,2kπ+π]
解得x∈[kπ-π/8,kπ+3π/8]k∈Z
这个是单调递增
单调递减是x∈[kπ+3π/8,kπ+7π/8]k∈Z