Perpendiculars to a Chord

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Let the chord CF intersect the diameter AB of a circle. Let D and E be the feet of the perpendiculars from A and B to CF. Then CD = EF.
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Contributed by: Jay Warendorff (March 2011)
After work by: Antonio Gutierrez
Open content licensed under CC BY-NC-SA
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The statement of the theorem is in Archimedes' Book of Lemmas: Proposition 13.
Permanent Citation
"Perpendiculars to a Chord"
http://demonstrations.wolfram.com/PerpendicularsToAChord/
Wolfram Demonstrations Project
Published: March 7 2011