已知函数f(x)=根号3sinxcosx+cos눀x+1⼀2,x属于R,求f(x)的递减区间

2024-11-30 09:44:20
推荐回答(2个)
回答1:

f(x)=√3sinxcosx+cos²x+1/2
=√3/2sin2x+1/2cos2x+1=sin(2x+π/6)+1,则递减区间是:2kπ+π/2≤2x+π/6≤2kπ+3π/2,得:kπ+π/6≤x≤kπ+2π/3,则减区间是:[kπ+π/6,kπ+2π/3],其中k∈Z
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回答2:

f(x)=√3sinxcosx+cos²x+1/2=√3/2 sin2x+1/2(2cos²x-1)+1=√3/2 sin2x+1/2cos2x+1
=cosπ/6sin2x+sinπ/6cos2x+1=sin(π/6+2x)+1
f(x)的递减区间:
2kπ+π/2≤π/6+2x≤2kπ+3π/2
2kπ+π/3≤2x≤2kπ+4π/3
kπ+π/6≤x≤kπ+2π/3