cos(x-pi/3)
/ pi\ cos|x - --| \ 3 /
d / / pi\\ --|cos|x - --|| dx\ \ 3 //
Let .
The derivative of cosine is negative sine:
Then, apply the chain rule. Multiply by :
Differentiate term by term:
Apply the power rule: goes to
The derivative of the constant is zero.
The result is:
The result of the chain rule is:
Now simplify:
The answer is: