Understand the difference between experimental verification of geometrical statements and geometric proof and confidently scaffold the process of writing geometric proofs.
This module addresses the major big idea of geometric reasoning, that is geometric proof. It contains a number of activities, including; exploring the proof of angle sum of a triangle in several ways, progressing to proof of congruence and similarity. There is an emphasis on correctly and clearly identifying and naming angles and lengths, reinforcing the formality required for a deductive proof. Participants might further explore with Geogebra. Teachers will be able to reinforce their understanding of the often complex nature of writing formal geometric proofs.
This module is one of four modules on Geometric Reasoning; the others are: plane shapes, congruence and similarity, and circle geometry.
Reasoning about geometric proof is based on some of the material found in AAMT’s Top Drawer Teachers.
Videos
Video: Geometric proof: Demonstration of the angle sum of a triangle
The video provides evidence to conjecture that the angle sum of a triangle is 180°.
Downloads
- Slides: Geometric proof (PPTX 1,005 KB)
- Facilitator Notes: Geometric proof (DOCX 184 KB)
- Worksheet 1: Geometric proof: Angle sum of a triangle (PDF 135 KB)
- Worksheet 2: Geometric proof: Geometry toolkit (PDF 310 KB)
- Worksheet 2 Solutions: Geometric proof: Geometry toolkit (PDF 344 KB)
- Handout 1: Geometric proof: Proving Pythagoras' theorem (PDF 202 KB)
- Handout 2: Geometric proof: Pythagoras' similarity proof (PDF 220 KB)
- Worksheet 3: Geometric proof: Proving congruence (PDF 118 KB)
- Worksheet 3 Solutions: Geometric proof: Proving congruence (PDF 248 KB)
- Handout 3: Geometric proof: Geometry checkups: Sample answers (PDF 207 KB)
- Handout 4: Geometric proof: Geometry checkups: Annotated version (PDF 435 KB)
