From: Bev Greco <bgreco@gasd.org>
To: Teacher2Teacher Public Discussion
Date: 2008060413:30:27
Subject: postulate vs theorem for corresponding angles

	
We are choosing a new text for our NYS Geometry course, and different
texts present 2 column proofs differently.  In our math department,
there is a disagreement as to whether we can use the corresponding
angles formed when 2 parallel lines are cut by a transversal as a
postulate rather than a theorem.  I can find it both ways in many
places.  We have always proven it as a theorem using an indirect
proof.  If we are to talk about true Euclidean proofs, is it incorrect
to use corresponding angles as a postulate rather than a theorem? 
Some teachers feel it is not obvious that corresponding angles formed
when 2 parallel lines are cut by a transversal are congruent.  Others
just feel that it is not acceptable under the title "Euclidean".  Any
ideas?

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