已知函数f(x)=根号3sinxcosx-sin눀x+1⼀2 1 求f(x)的最小正周期值 2 求f(x)的单调递增区间

3 求f(x)在[0,π/2]上的最值及取最值为x的值
2025-03-15 08:01:02
推荐回答(1个)
回答1:

解:
(1)
f(x)=√3sinxcosx-sin²x+½
=½[√3·(2sinxcosx)+(1-2sin²x)]
=½[√3sin(2x)+cos(2x)]
=(√3/2)sin(2x)+½cos(2x)
=sin(2x)cos(π/6)+cos(2x)sin(π/6)
=sin(2x+π/6)
最小正周期T=2π/2=π
(2)
2kπ-π/2≤2x+π/6≤2kπ+π/2,(k∈Z)时,函数单调递增
此时,kπ-π/3≤x≤kπ+π/6,(k∈Z)
函数的单调递增区间为[kπ-π/3,kπ+π/6],(k∈Z)
(3)
x∈[0,π/2],π/6≤2x+π/6≤7π/6
sin(7π/6)≤sin(2x+π/6)≤sin(π/2)
-½≤sin(2x+π/6)≤1
2x+π/6=π/2时,即x=π/6时,函数取得最大值,f(x)max=1
2x+π/6=7π/6时,即x=π/2时,函数取得最小值,f(x)min=-½

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