f(x)=cos(x+π/6）cos(x-2π/3)+sin(x+π/6)sin(x+π/3) 求函数F（X）的单调递减区间
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f(x)=cos(x+π/6）cos(x-2π/3)+sin(x+π/6)sin(x+π/3)求函数F（X）的单调递减区间f(x)=cos(x+π/6）cos(x-2π/3)+sin(x+π/6)si
f(x)=cos(x+π/6）cos(x-2π/3)+sin(x+π/6)sin(x+π/3) 求函数F（X）的单调递减区间
f(x)=cos(x+π/6）cos(x-2π/3)+sin(x+π/6)sin(x+π/3) 求函数F（X）的单调递减区间
f(x)=cos(x+π/6）cos(x-2π/3)+sin(x+π/6)sin(x+π/3) 求函数F（X）的单调递减区间
sin(x+π/3)=-sin(x+π/3-π)=-sin(x-2π/3)
f(x)=cos(x+π/6)cos(x-2π/3)+sin(x+π/6)sin(x+π/3)=cos(x+π/6)cos(x-2π/3)-sin(x+π/6)sin(x-2π/3)
=cos[(x+π/6)+(x-2π/3)]
=cos(2x-π/2)
cosx单调递减区间为[2kπ,2kπ+π]
∴f(x)单调递减区间为[kπ+π/4,kπ+3π/4]
f(x)=-cos(x+5π/6),递减区间为-5π/6+2πk<=x<=π/6+2πk为什么？步骤是什么？不是，是f(x)=-cos(2x+π/2)=sin(x),由于cos(x-2π/3)=-cos(x-2π/3+π)=-cos(x+π/3)，所以f(x)=-cos(x+π/6）cos(x+π/3)+sin(x+π/6)sin(x+π/3)=-cos(2x+π/2)=sin(2x),接下来就是...
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f(x)=-cos(x+5π/6),递减区间为-5π/6+2πk<=x<=π/6+2πk
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