MathDB
BR = 2XY wanted, AR = BP, AQ = AB ,tangent to circumcircle related

Source: Switzerland - Swiss ΜΟ 2017 p5

July 14, 2020
geometrycircumcircleequal segmentstangent

Problem Statement

Let ABCABC be a triangle with AC>ABAC> AB. Let PP be the intersection of BCBC and the tangent through AA around the triangle ABCABC. Let QQ be the point on the straight line ACAC, so that AQ=ABAQ = AB and AA is between CC and QQ. Let XX and YY be the center of BQBQ and APAP. Let RR be the point on APAP so that AR=BPAR = BP and RR is between AA and PP. Show that BR=2XYBR = 2XY.