# A Concurrency of Lines through Points of Tangency with Excircles

Requires a Wolfram Notebook System

Interact on desktop, mobile and cloud with the free Wolfram Player or other Wolfram Language products.

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

## Snapshots

## Details

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

## Permanent Citation

"A Concurrency of Lines through Points of Tangency with Excircles"

http://demonstrations.wolfram.com/AConcurrencyOfLinesThroughPointsOfTangencyWithExcircles/

Wolfram Demonstrations Project

Published: September 24 2008