求cos^2x-sinxcosx-1/2单调增区间

求cos^2x-sinxcosx-1/2单调增区间
求cos^2x-sinxcosx-1/2单调增区间

求cos^2x-sinxcosx-1/2单调增区间
f（x）=(2cos^2x-1)/2-2sinxcosx/2
=(cos2x-sin2x)/2
=√2/2*cos(2x+π/4)
所以2kπ-π

先求导，令其等于0解出X 。

y=sinxcosx+cos^2x-1/2
=(cos2x-sin2x)/2
=√2/2*cos(2x+π/4)
所以2kπ-π<=2x+π/4<=2kπ
kπ-5π/8<=x<=kπ-π/8曾区间【kπ-5π/8，kπ-π/8】 k∈Z符号不对啊sinxcosx是负的
y=-sinxcosx+cos^2x-1/2
=(cos2x-sin...

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y=sinxcosx+cos^2x-1/2
=(cos2x-sin2x)/2
=√2/2*cos(2x+π/4)
所以2kπ-π<=2x+π/4<=2kπ
kπ-5π/8<=x<=kπ-π/8曾区间【kπ-5π/8，kπ-π/8】 k∈Z

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