6.3 - Proving a Quadrilateral is a Parallelogram

6.3 - Proving a Quadrilateral is a Parallelogram

By Steve Dull

Recall practice

Objective:

To prove a quadrilateral is a parallelogram.

Time to sharpen up our logical thinking skills...

Previously

You have written two-column proofs for algebra equations, for angle and segment measure, for angle pairs when parallel lines were cut by a transversal, and for triangle congruence.

Poll

Which image best sums up how you feel about your skills at writing proofs?

Today we'll use what you have learned previousy about writing proofs, and about triangle congruence and parallel lines cut by a transversal to prove a quadrilateral is a parallelogram.

What statement goes first?:

Multiple Choice

The "Given" information goes first. What statement should you write next?

• $$AC\cong AC$$  

• $$\Delta BAC\ \cong\Delta DCA$$  

• $$BA\ \parallel\ CD$$  

• ABCD is a parallelogram

I'll bring it home:

​Feel free to work with two or three students nearby you.

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Your turn:

One more:

Lets's wrap up by working through three proofs on your own. Check in with your classmates with questions. I'll make my way around the room and peek over shoulders.

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​Good work!