MathDB
Externally tangent circles and midpoints

Source: Moldova TST 2012

February 19, 2016
geometry

Problem Statement

Let C(O1),C(O2)C(O_1),C(O_2) be two externally tangent circles at point PP. A line tt is tangent to C(O1)C(O_1) in point RR and intersects C(O2)C(O_2) in points A,BA,B such that AA is closer to RR than BB is. The line AO1AO_1 intersects the perpendicular to tt in BB at point CC, the line PCPC intersects ABAB in QQ. Prove that QO1QO_1 passes through the midpoint of BCBC.