先变形,由诱导公式cosα=sin(α+π/2)
y=cos(2x-π/6)=sin(2x-π/6+π/2)=sin(2x+π/3)
y=cos(2x-π/6）即y=sin(2x+π/3)→（横坐标伸长两倍)得y=sin(x+π/3）
→向右平移π/3个单位得y=sinxy=cos(2x-π/6)即y=sin(2x+π/3) 怎么得到的？cos(2x-π/6)=sin(2x-π/6+π/2)=sin(2x+π/3)