Wednesday, October 27, 2010

Wed 10/27/10

HW: Prove theorem 3-2 and 3-3.
Make sure you write the entire theorems, draw and label its diagram, state the given and prove with respect to the diagram, and then write a 2-column proof.

Theorem 3-2: If two parallel lines are cut by a transversal, then each pair of consecutive interior angles is supplementary.

Theorem 3-3: If two parallel lines are cut by a transversal, then each pair of alternate exterior angles is congruent.

Today: We did not go over last night's HW. We will do it tomorrow. I handed out the instructions for 3 constructions. We practiced the construction of creating 2 parallel lines (continued from yesterday). Please know this construction and why it works perfectly!

We covered 2 postulates (converses):
Postulate 3-1: If two parallel lines are cut by a transversal, then each pair of corresponding angles is congruent.
Postulate 3-4: If two lines are cut by a transversal and a pair of corresponding angles are congruent, then the lines are parallel.
Understand them! Why are they true? Why are they postulates?
Tomorrow: More proofs of theorems! woo hoo!

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