Finding the (x + π / 3) power series of function cosx

Finding the (x + π / 3) power series of function cosx

cosx=cos(x+π/3-π/3)=cos(x+π/3)/2+sin(x+π/3)*√3/2
In this way, t = (x + π / 3) can be brought into the above formula, and cost and Sint are commonly used series, so the answer will come out naturally