Answer
$y=-1+\sin x$
Work Step by Step
The graph is that of $y=\sin x$ except that it has been translated one unit down.
Therefore, the graph is of the form $y=c+\sin x$. According to the rules of translating graphs, the translation is $c$ units up if $c$ is greater than zero. Conversely, the translation is $|c|$ units down if $c$ is less than zero.
Since the graph is that of $y=\sin x$ which has been translated one unit down, the equation of the graph is $y=-1+\sin x$.