Problem

Problem

Let InI_n is the area of nn-sided regular polygon inscribed in a circle of unit radius and OnO_n be the area of the polygon circumscribing the given circle. Then, prove that In=On2(1+1−(2InOn)2)I_n = \frac{O_n}{2} \left( 1 + \sqrt{1 - \left(\frac{2I_n}{O_n}\right)^2} \right) .

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