MathDB
2 tangents of different circles intersect on a line

Source: 2023 Czech-Polish-Slovak Match Junior, Team p4 CPSJ

May 5, 2024
geometrycollinear

Problem Statement

In triangle ABCABC, the points MM and NN are the midpoints of the sides ABAB and ACAC, respectively. The bisectors of interior angles ABC\angle ABC and BCA\angle BCA intersect the line MNMN at points PP and QQ, respectively. Let pp be the tangent to the circumscribed circle of the triangle AMPAMP passing through point PP, and qq be the tangent to the circumscribed circle of the triangle ANQANQ passing through point QQ. Prove that the lines pp and qq intersect on line BCBC.