Guidelines: Developing a Proof
Proofs delve into the logic side of geometry. Students begin with a set of "givens" and must apply logical operations to arrive at certain conclusions. One type of proof uses a set of "transformations" to geometric figures to show that they are equivalent (or not).
Before students create their own proofs, lead them through the examples on page 385.
Then teach students how to analyze the prompt and extract the "givens." Equip them with the four main transformations—translating, reflecting, rotating, and dilating. Then let students experiment with the figures, working out their proofs.
Once they are ready to write their proofs, lead students through the process.
Also, provide them the Checklist for Revising and Editing Proofs. Of course, they will not use this formal checklist most times when they are working with proofs, but it can teach them the kinds of questions they can ask themselves to improve their work.