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Geometry - 2016 Taiwan TST Round 1 Quiz 1 Problem 2

Source: 2016 Taiwan TST Round 1 Quiz 1 Problem 2

March 29, 2016
geometry

Problem Statement

Circles O1O_1 and O2O_2 intersects at two points BB and CC, and BCBC is the diameter of circle O1O_1. Construct a tangent line of circle O1O_1 at CC and intersecting circle O2O_2 at another point AA. We join ABAB to intersect O1O_1 at point EE, then join CECE and extend it to intersect circle O2O_2 at point FF. Assume that HH is an arbitrary point on the line segment AFAF. We join HEHE and extend it to intersect circle O1O_1 at point GG, and join BGBG and extend it to intersect the extended line of ACAC at point DD. Prove that AHHF=ACCD\frac{AH}{HF}=\frac{AC}{CD}.