已知函数f(x)=sin(2x+π/6)+sin(2x-π/6)+2cos²x

1个回答

  • 1.

    f(x)=sin(2x+6/π)+2sin^2 x

    =(√3/2)sin2x+(1/2)cos2x+1-cos2x

    =(√3/2)sin2x-(1/2)cos2x+1

    =sin(2x-π/6)+1

    所以f(x)的最小正周期为π;

    2.

    2x-π/6=π/2+2kπ ,k∈Z

    即x=π/3+kπ ,k∈Z

    f(x)=sin(2x-π/6)+1最大值为2,

    x 的取值集合为{x|x=π/3+kπ ,k∈Z}

    3.

    -π/2+2kπ≤2x-π/6≤π/2+2kπ,k∈Z时

    即-π/6+kπ≤x≤π/3+kπ ,k∈Z时f(x)单调递增;

    π/3+kπ≤x≤5π/6+kπ ,k∈Z时f(x)单调递减;

    区间为……

    (注:“/”为分号,左边为分子,右边为分母)