[header] How to determine a square and circle of equal area [title] Let r1 ^ 2 represent the area of the square, a (s). [title] Let πr2 ^ 2 = the area of the circle, a (c). [title] Set a (s) = a (c) via r1 ^ 2 = πr2 ^ 2. 
[title] Then r1 ^ 2/r2 ^ 2 = π and r1/r2 = sqrt (π). [title] Given either r1 or r2, we can determine the other one.