Answer
The graph of $r = k$, $k \gt 0$ will be a series of concentric circles with center at the origin and directed distance k.
Work Step by Step
Now $r = \pm\sqrt{x^2 + y^2}$
But since, $r = k$, $k \gt 0$, it implies that $r \gt 0$,
therefore $r = \sqrt{x^2 + y^2}$
The graph of $r = k$, $k \gt 0$ will be a series of concentric circles with center at the origin and directed distance k.
