where there is equality if and only if the quadrilateral is a right kite. This is a direct
consequence of Corollary 2 and the formula K = rs for the area of a tangential
quadrilateral. To derive this inequality was a part of Problem 1203 in Crux Mathematicorum
according to [10, p.39]. Another part of that problem was to prove that
in a bicentric quadrilateral, the product of the sides satisfies