已知函数f(x)=2√3sinx·cosx+cos^2x-sin^2x-1(x∈R)

(1)求单调递增区间(2)若x∈[-5pai/12,pai/3]第二步要求详细点
2024-12-19 12:56:10
推荐回答(1个)
回答1:

答:
f(x)=2√3sinxcosx+cos²x-sin²x-1
=√3sin2x+cos2x-1
=2*[sinx(√3/2)+cos2x(1/2)-1
=2sin(x+π/6)-1

(1)f(x)=2sin(x+π/6)-1的单调增区间满足:-π/2+2kπ<=x+π/6<=π/2+2kπ
所以:函数的单调增区间为[2kπ-2π/3,2kπ+π/3],k∈Z

(2)若-5π/12<=x<=π/3
则:-π/4<=x+π/6<=π/2
所以:-√2/2<=sin(x+π/6)<=1
所以:-√2<=2sin(x+π/6)<=2
所以:-1-√2<=f(x)<=1
所以:f(x)的值域为[-1-√2,1]