MathDB
2017-2018 Spring OMO Problem 23

Source:

April 3, 2018
Online Math Open

Problem Statement

Let ABCABC be a triangle with BC=13,CA=11,AB=10BC=13, CA=11, AB=10. Let A1A_1 be the midpoint of BCBC. A variable line \ell passes through A1A_1 and meets AC,ABAC,AB at B1,C1B_1,C_1. Let B2,C2B_2,C_2 be points with B2B=B2C,B2C1AB,C2B=C2C,C2B1ACB_2B=B_2C, B_2C_1\perp AB, C_2B=C_2C, C_2B_1 \perp AC, and define P=BB2CC2P=BB_2\cap CC_2. Suppose the circles of diameters BB2,CC2BB_2, CC_2 meet at a point QA1Q\neq A_1. Given that QQ lies on the same side of line BCBC as AA, the minimum possible value of PBPC+QBQC\dfrac{PB}{PC}+\dfrac{QB}{QC} can be expressed in the form abc\dfrac{a\sqrt{b}}{c} for positive integers a,b,ca,b,c with gcd(a,c)=1\gcd (a,c)=1 and bb squarefree. Determine a+b+ca+b+c.
Proposed by Vincent Huang