Answer
$f^{\prime}(x)= 2 \sin (-2x+5)$
Work Step by Step
We have: $f(x)=\cos (-2x+5)$
We need to differentiate both sides with respect to $x$.
$f^{\prime}(x)= -\sin (-2x+5) \dfrac{d}{dx} (-2x+5)\\=-\sin (-2x+5) \times (-2)$
Therefore, $f^{\prime}(x)= 2 \sin (-2x+5)$
