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geometry junior
Problem
A square with side length 2 and a circle share the same center. The total area of the regions that are inside the circle and outside the square is equal to the total area of the regions that are outside the circle and inside the square. What is the radius of the circle? 
(A)
(B)
(C)
(D)
Solution
Let the region within the circle and square be . In other words, it is the area inside the circle the square. Let be the radius. We know that the area of the circle minus is equal to the area of the square, minus . We get: So the answer is .
Final answer
A