已知函数f(x)=cos(2x-π/3)+2sin(x-π/4sin(x+π/4)(1)求函数f(x)的最小正周期和图像的对称轴方程(2)求函
(2)求函数f(x)在区间[-π/12,π/2]上的值域
人气:341 ℃ 时间:2019-08-20 08:04:02
解答
题目没有打对,至少少了半边括号已知函数f(x)=cos(2x-π/3)+2sin(x-π/4)sin(x+π/4)f(x)=cos(2x-π/3)+2sin(x-π/4)sin(x+π/4) =cos(2x-π/3)+cos[(x-π/4)-(x+π/4)]-cos[(x-π/4)+(x+π/4)] =cos(2x-π/3)-cos2x+cos(-π/2) =cos(2x-π/3)-cos2x =-2sin(2x-π/6)sin(-π/6) =sin(2x-π/6)故最小正周期为π令2x-π/6=kπ(k∈Z),解得:x=(k/2+1/12)π这就是图像的对称轴方程由x∈[-π/12,π/2]得2x-π/6∈[-π/3,5π/6]由π/2∈[-π/3,5π/6]函数最大值为1最小值为sin(-π/3)=-√3/2
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