MathDB
Orthocenter geo with tangencies

Source: St Petersburg 2022 11.5

September 28, 2022
geometry

Problem Statement

Altitudes AA1,BB1,CC1AA_1, BB_1, CC_1 of acute triangle ABCABC intersect at point HH. On the tangent drawn from point CC to the circle (AB1C1)(AB_1C_1), the perpendicular HQHQ is drawn (the point QQ lies inside the triangle ABCABC). Prove that the circle passing through the point B1B_1 and touching the line ABAB at point AA is also tangent to line A1QA_1Q.