Question

已知函数f(x)=sin(x-π/6)(x∈R),则函数Y=f（x）的表达式可以改写成f（x）=cos（x-π/3）吗?

Answer 1

Y=f（x）=sin(x-π/6）=cos[π/2-(x-π/6)]=cos(2π/3-x)=cos(x-2π/3)

=-cos(x+π/3)

不能改写成f（x）=cos（x-π/3）