Tangent Circles and Parallel Diameters

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Let two circles with diameters BC and DE be tangent at point A. If BC || DE, then A, C, and E are collinear.
Contributed by: Jay Warendorff (March 2011)
After work by: Antonio Gutierrez
Open content licensed under CC BY-NC-SA
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Details
The statement of the theorem is in Archimedes Book of Lemmas: Proposition 1.
Permanent Citation
"Tangent Circles and Parallel Diameters"
http://demonstrations.wolfram.com/TangentCirclesAndParallelDiameters/
Wolfram Demonstrations Project
Published: March 7 2011