已知函数f(x)=√3sinx^2+sinxcosx

3个回答

  • (1) ∵f(x)=√3sin²x+sinxcosx

    =(√3/2)*(2sin²x-1+1)+(1/2)*2sinxcosx

    =(√3/2)*(-cos2x+1)+(1/2)*(sin2x)

    =(1/2)*sin2x/-(√3/2)*cos2x+√3/2

    =sin(2x-π/3)+√3/2

    ∴ f(24π/6)=f(4π)=sin(2*4π-π/3)+√3/2

    =sin(8π-π/3)+√3/2

    =sinπ/3+√3/2=√3

    (2) g(x)=f(x)+√3/2

    =sin(2x-π/3)+√3/2+√3/2

    =sin(2x-π/3)+√3

    当 2x-π/3=2kπ-π/2,即x=kπ-π/12(k∈z)时,g(x)取得最小值

    此时,最小值为-1+√3

    (3) f(x)单调递增区间为

    2kπ≤2x-π/3≤2kπ+π/2

    或 2kπ+3π/2≤2x-π/3≤2kπ+2π (k∈z)

    解,得

    x∈[kπ+π/6,kπ+5π/12]或x∈[kπ+11π/12,kπ+7π/6] (k∈z)