Three Concyclic Sets of Points Associated with the Orthic Triangle

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Let ABC be an acute triangle and H its orthocenter. Let A', B', and C' be the feet of the altitudes from A, B, and C. Let L, M, and N be the contact points of the orthic triangle with its incircle with L on A'B', M on A'C', and N on B'C'. Then A', M, H, L are concyclic as are B', L, H, N and C', M, H, N.

Details

The statement of the theorem is in Problem 136. Orthic Triangle, Altitudes, Orthocenter, Incenter, Perpendicular, Concyclic Points.

External Links

Concyclic (Wolfram MathWorld)
Incircle (Wolfram MathWorld)
Orthocenter (Wolfram MathWorld)

Permanent Citation

Jay Warendorff, Antonio Gutierrez
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​"Three Concyclic Sets of Points Associated with the Orthic Triangle"​
​http://demonstrations.wolfram.com/ThreeConcyclicSetsOfPointsAssociatedWithTheOrthicTriangle/​
​Wolfram Demonstrations Project​
​Published: March 7, 2011