What is reason 2 in the following proof?
Given: ABCD is a parallelogram with diagonals AC and DB intersecting at point E.
Prove:

Question

What is reason 2 in the following proof?
Given: ABCD is a parallelogram with diagonals AC and DB intersecting at point E.
Prove: <ABD is congruent to < CDB
Statements Reasons

ABCD is a parallelogram 1. Given
    Segment AB is parallel to Segment DC 2.
    < ABD is congruent to <CDB 3.

1)

Alternate Interior angles
	2)

Properties of parallelograms
	3)	
SSS
	4)	
CPCTC

anonymous · Answer

I think the question is typed incorrectly.  Can you check the question again and make sure you have it right?

anonymous · Answer

thats what i said but they said its rite

anonymous · Answer

Ok...I see what it's saying now.  I didn't get the question as it was formatted, but now I see that you are given four choices for tha answer.

You can elliminate choice 3) SSS because that would be a justification for triangles being congruent.  Choice 4) says that parts of congruent triangles have equal corresponding parts.  SInce you haven't established congruent triangles, this doesn't really work either.

That leaves 1) and 2).  Alternate Interior angles are equal *if* the lines (cut by a transversal) are parallel. This can be used to justify parallel lines if you've already established the angles are equal (which you don't have until line 3...using the fact th lines are parallel). Therefore 1) is no good.

That leaves choice 2) Properties of a parallelogram...which establishes that opposite sides are parallel.

anonymous · Answer

It then follows that the justification for step 3. is choice 1) Alternate Interior angles are equal.