Let .
Apply the power rule: goes to
Then, apply the chain rule. Multiply by :
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:
The result of the chain rule is:
Now simplify:
The answer is:
-2*cos(x - 7)*sin(x - 7)
/ 2 2 \ 2*\sin (-7 + x) - cos (-7 + x)/
8*cos(-7 + x)*sin(-7 + x)