Answer
The radius is $\sqrt {10}$.
Work Step by Step
Please see the graph of the circle. The maximum $y$ value is $.162$, and the minimum $y$ value is $-6.162$.
If we add the absolute values of the minimum and maximum, we get $6.326$. This is the diameter of the circle. If we divide this by 2 (to get the radius), we get 3.162. If we square this number, we get a result of 9.998 (or 10).
Since we squared our result, we find that the radius is $\sqrt {10}$.
