How do you find the radius of a circle with area of 63.6 sq. feet?

Circle    $${\mathtt{A}} = {{\mathtt{r}}}^{{\mathtt{2}}}{\mathtt{\,\times\,}}{\mathtt{\pi}}$$        =>     $${\mathtt{r}} = {\sqrt{{\frac{{\mathtt{A}}}{{\mathtt{\pi}}}}}}$$

 

r =  $${\sqrt{{\frac{{\mathtt{63.6}}}{{\mathtt{\pi}}}}}} = {\mathtt{4.499\: \!389\: \!820\: \!996\: \!742}}$$   feet

 

http://web2.0calc.com/formulary/math/geometry/circle