What is the corresponding function of the new image after the image translation vector a = (π / 4,0) of the function y = cos (2 / 3x + π / 6)

What is the corresponding function of the new image after the image translation vector a = (π / 4,0) of the function y = cos (2 / 3x + π / 6)

Let a point (x, y) on the image of a known function be (x1, Y1) after the translation of vector a, then
x1=x+π/4,y1=y
∴x=x1-π/4,y=y1
y=cos(2/3x+π/6)
∴y1=cos[2/3(x1-π/4)+π/6]=cos2π/3x1
The function is y = Cos2 π / 3x