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Team Selection Test for JBMO 2024

Turkey 2024 geometry

Problem

Let be an acute triangle, be the midpoint of the side and be the foot of the altitude from . Let be a point on the segment such that . Let the second intersection point of the circumcircle of and line be . Let the second intersection point of the circumcircle of and line be . Prove that .

problem
Solution
Since , , , are concyclic we have and hence is a right triangle. Since lies on the circle centered at and , we can see that is tangent to the circumcircle of . Using the power of the point with respect to the circles and we get and from the Euclid relations in the triangle we are done.

Techniques

Cyclic quadrilateralsTangentsRadical axis theoremAngle chasing