函数y=cos(x-π/8)(x∈【π/6.2π/3】)的最小值是

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函数y=cos(x-π/8)(x∈【π/6.2π/3】)的最小值是

函数y=cos(x-π/8)(x∈【π/6.2π/3】)的最小值是
函数y=cos(x-π/8)(x∈【π/6.2π/3】)的最小值是

函数y=cos(x-π/8)(x∈【π/6.2π/3】)的最小值是
∵π/6≤x≤2π/3
∴π/6-π/8≤x-π/8≤2π/3-π/8
∴π/24≤x-π/8≤13π/24
∵13π/24>12π/24=π/2
∴y的最小值为负值=cos(13π/24)=-sin(π/24)≈-0.1305

y= cos(x-π/8)
等于是将cosx的图像往右边移动了π/8个单位
那么这样,最小值-1应该对应的是 π + π/8 = 9/8π > 2/3π
所以在区间[π/6, 2/3π] 内
y最大值 = cos(π/6 - π/8) = cos(π/24)
y最小值 = cos(2/3π - π/8) = cos(13π/24)