MathDB
Length of BC must be $(12+9\sqrt{15})/5$

Source: Bstat-Bmath 2017: Problem 2

May 14, 2017
geometry

Problem Statement

Consider a circle of radius 66. Let B,C,DB,C,D and EE be points on the circle such that BDBD and CECE, when extended, intersect at AA. If ADAD and AEAE have length 55 and 44 respectively, and DBCDBC is a right angle, then show that the length of BCBC is 12+9155\frac{12+9\sqrt{15}}{5}.