Solve the Problem $$\text { Solve the formula } r = \sqrt { \frac { 2 \mathrm {~A} } { \theta } } \text { for } \theta \text {. }$$

Solve the problem.
- $$\text { Solve the formula } r = \sqrt { \frac { 2 \mathrm {~A} } { \theta } } \text { for } \theta \text {. }$$