Proofs may be as easy as 1, 2, 3 ... maybe. Pupils participate in creating four example proofs. The presentation uses a list of geometric properties to develop the proofs by filling in both the statements and reasons. Scholars practice writing their own proofs, concentrating mainly on algebraic proofs.

Concepts

proofs, two-column proofs, geometric proofs, algebraic properties, vertical angles, parallel lines with a transversal, corresponding angles, supplementary angles

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Instructional Ideas

• Make a point that not all correct proofs look the same way

Classroom Considerations

• Third section in a four-part unit on geometric proofs
• Assumes knowledge of angle relationships such as supplementary and those associated with parallel lines

• This video is hosted on YouTube

Pros

• Shows a second way to write a particular proof
• Includes additional practice if needed

Cons

• None

Common Core

SL.9-10.2 SL.11-12.2 MP3 MP6 HSA-REI.A.1 HSG-CO.C.9