A Concurrency of Lines through Points of Tangency with Excircles

Let ABC be a triangle with orthocenter H. Let be the point of tangency of CA with the excircle opposite A, and similarly define , , , , and . Let , , and . Let , , and . Then AA', BB', and CC' as well as AA'', BB'', and CC'' meet at H.

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See the paper "Synthetic proof of Paul Yiu's excircles theorem" available on Darij Grinberg's home page.
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