Answer
The variable k in the equation $y = k + \sin x$ determines the vertical shift of the graph.
$y = 0 + \sin x$ -> no vertical shift
$y = -2 + \sin x$ -> 2 units vertical shift from the original position
$y = -4 + \sin x$ -> 2 units vertical shift from the original position
Work Step by Step
See below graph from reference:
