Answer
$\cos (ax+b)$
Work Step by Step
Our aim is to solve the function $F(x)=\dfrac{1}{a} \sin (ax+b)+C$
We differentiate both sides with respect to $x$.
$F^{\prime}(x)=\dfrac{1}{a}\dfrac{d}{dx}[ \sin (ax+b)]+\dfrac{d}{dx}(C)$
or, $=\dfrac{1}{a}\cos (ax+b) \dfrac{d}{dx} (ax+b)+\dfrac{d}{dx}(C)$
or, $=\cos (ax+b)$
