函数y=1/2sin(2x + pai/3)-sinxcosx的单调递减区间?

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函数y=1/2sin(2x + pai/3)-sinxcosx的单调递减区间?
函数y=1/2sin(2x + pai/3)-sinxcosx的单调递减区间?

函数y=1/2sin(2x + pai/3)-sinxcosx的单调递减区间?
y=1/2sin(2x+π/3)-sinxcosx
=1/2(1/2sin2x+√3/2cos2x)-1/2sin2x
=1/2(-1/2sin2x+√3/2cos2x)
=1/2(cosπ/6cos2x-sinπ/6sin2x)
=1/2cos(2x+π/6)
当2x+π/6∈[0+2kπ,π+2kπ](k∈Z)时,y单调递减
即0+2kπ≤2x+π/6≤π+2kπ
-π/12+kπ≤x≤5π/12+kπ
y的单调递减区间是[-π/12+kπ,5π/12+kπ](k∈Z)

y=1/2sin(2x + π/3)-sinxcosx
=1/2sin(2x + π/3)-1/2sin2x
=√3/4cos2x-1/4sin2x
=1/2sin(π/3-2x)
2kπ+π/2<π/3-2x<2kπ+3π/2
2kπ+π/6<-2x<2kπ+7π/6
kπ+π/12<-xkπ-π/12>x>kπ-7π/12