Today is about getting more and more kids fluent in their ability to prove this fact, and so I push a few kids to come up to the board to present their proof, and to get evaluated by their peers. We use two simple questions to evaluate:
1. Is the logic correct?
2. Is the presentation clear and understandable?
It's nice to end the unit with arranging 3 copies, because it actually is a bit easier than the other proofs and provides a nice sense of closure to the proof-writing. We engage in error analysis right away - is there anything wrong with this picture? - and also focus on using different types of triangles - equilateral, scalene, isosceles, right triangles, etc. -- to see how they each are governed by the same principle. Pretty powerful to get kids to see this.
In terms of error analysis, I often use a scalene triangle and put two of the same angles together with a third, which does not form a straight line. I ask a fairly "naked" question - what is going on here? - and I see where the discussion takes us.
Tonight's homework is a take-home assessment. Assessment #13 Transversals and Triangles is to be completed at home.
I did a lot of take-home assessments in this school year, to save instructional days, particularly in light of missing 5 days from Hurricane Sandy. In the future, I would likely complete this assessment as an in-class assessment.