Lines Parallel to the Sides of a Triangle

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Let ABC be a triangle and let the angle bisectors at A, B, and C intersect the opposite sides at points P, Q, and R. Draw lines from P, Q, and R parallel to AB, BC, and AC that intersect AC, AB, and BC at P', Q', and R'. Then .
Contributed by: Jay Warendorff (March 2011)
After work by: Paul Yiu
Open content licensed under CC BY-NC-SA
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Details
The statement of the theorem is in "Notes on Euclidean Geometry" by Paul Yiu, p. 90.
Permanent Citation
"Lines Parallel to the Sides of a Triangle"
http://demonstrations.wolfram.com/LinesParallelToTheSidesOfATriangle/
Wolfram Demonstrations Project
Published: March 7 2011