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Re: Exterior Angle without parallels?
Posted:
Dec 21, 2007 2:18 PM


Jacobs proceeds in the footsteps of Euclid who proved the Exterior Angle Theorem as I.16 but used the Parallel Postulate in I.29 for the first time.
See a discussion at
http://www.cuttheknot.org/fta/Eat/EAT.shtml
A. Bogomolny



