Curated OER
Indirect Proof and Inequalities in one Triangle
In this geometry worksheet, 10th graders complete an indirect proof and order the sides or angles of a triangle. Also, students determine if a triangle can have sides with the given lengths. The two page worksheet contains twelve...
Oswego City School District
Regents Exam Prep Center: Indirect Euclidean Proofs
This Oswego City School District Regents Exam Prep site shows you how to proof something by showing that it is false. This look at indirect proofs includes a practice and a teacher resource page, which features a warm-up activity.
Kent State University
Kent State University: Indirect Proofs, Michael Byron
Use this site to explore an excellent discussion of indirect proofs. The site explains in detail why such a method works as a proof and gives steps to obtain such a proof.
CK-12 Foundation
Ck 12: Geometry: Indirect Proof in Algebra and Geometry
[Free Registration/Login may be required to access all resource tools.] This concept teaches students how to write an indirect proof and provides examples of indirect proofs in Algebra and Geometry.
CK-12 Foundation
Ck 12: Geometry: Indirect Proof in Algebra and Geometry
[Free Registration/Login may be required to access all resource tools.] Write algebraic and geometric indirect proofs.
CK-12 Foundation
Ck 12: Geometry: Types of Reasoning Study Guide
[Free Registration/Login may be required to access all resource tools.] Reasoning is a fundamental part of geometric proofs. There are several types of reasoning, many of which we innately and naturally picked up. However, the different...
CK-12 Foundation
Ck 12: Geometry: Proofs Study Guide
[Free Registration/Login may be required to access all resource tools.] This study guide reviews proofs: algebraic proof, properties of congruence, and geometric proofs (two-column).
University of Cambridge
University of Cambridge: Nrich: Code Breaker
Do your logic skills need sharpening? Use the interactive code breaker to at this one page website to do just that! The solution is available to double check your solution.