Question

函数f(x)=cos(x+π/6),x∈[-π/2,π/2]的值域是

Answer 1

f(x) = cos(x+π/6) x ∈ [-π/2,π/2] = [-90°,90°]

f(x) = cos(x+π/6) x+π/6 ∈ [-π/3,2π/3] = [-60°,120°]

cos(-60°) = 1/2 最左端

cos(0°) = 1 中间典型值 ----也是最大值

cos(90°) = 0 中间典型值

cos(120°) = -1/2 最右端 ----也是最小值