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已知:f(x)=2根号3cos^2 x+sinx乘以2cosx-根号3
求:1.f(x)的最小正周期.
2.f(x)的单调区间.
人气:479 ℃ 时间:2020-01-31 10:36:12
解答
∵f(x)=2√3cos² x+2sinxcosx-√3
=√3(1+cos2x)+sin2x-√3
=√3cos2x+sin2x
=2sin(2x+π/3)
(1)∴.f(x)的最小正周期T=2π/2=π
(2)由2kπ-π/2=≤2x+π/3≤2kπ+π/2,
即kπ-5π/12≤x≤kπ+π/12
由 2kπ+π/2≤2x+π/3≤2kπ+3π/2,即kπ+π/12≤x≤kπ+7π/12 ;
∴.f(x)的单调增间为:[kπ-5π/12,kπ+π/12]
单调减区间为:[kπ+π/12,kπ+7π/12];k∈Z
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