Subject: Re: [HM] When is Playfair's postulate important?
From: Samuel S. Kutler (s-kutler@sjca.edu)
Date: Mon Jan 10 2000 - 06:03:26 EST
Daina:
You ask
> ...
> Where do we ever care that parallel (non-intersecting) lines are unique?
> Is there any constuction that needs this result?
You will never be able to prove, for example, that the sum of the angles of
a triangle equal two right angles without that result. Lobachevsky showed
that, and before him Gauss knew that result.
Best wishes from Annapolis,
Sam Kutler
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