MathDB
2021 Geo #4: Trapezoidzzzz

Source:

May 30, 2021
geometry

Problem Statement

Let ABCD be a trapezoid with ABCD,AB=5,BC=9,CD=10,AB \parallel CD, AB = 5, BC = 9, CD = 10, and DA=7DA = 7. Lines BCBC and DADA intersect at point EE. Let MM be the midpoint of CDCD, and let NN be the intersection of the circumcircles of BMC\triangle BMC and DMA\triangle DMA (other than MM). If EN2=abEN^2 = \tfrac ab for relatively prime positive integers aa and bb, compute 100a+b100a + b.