Answer
$a=2$, $b=\frac{1}{2}$ and $c=0$
Work Step by Step
From the graph, since the graph from origin, the graph is then upward, and the amplitude is $2$, $a=2$.
Rewriting the function $f(x)=a\sin b\left(x-\frac{c}{b}\right)$ and from the graph, the period is $4\pi$:
$$period=\frac{2\pi}{b}$$ $$b=\frac{2\pi}{period}=\frac{2\pi}{4\pi}=\frac{1}{2}$$
From the graph, there is no shift:
$$\frac{c}{b}=0$$ $$c=0$$
Thus, $a=2$, $b=\frac{1}{2}$ and $c=0$.
