A Concurrency of Lines through Points of Tangency with Excircles

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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.

Contributed by: Jay Warendorff (September 2008)
After work by: Paul Yiu
Open content licensed under CC BY-NC-SA



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

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