National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Faq About Proofs
This site provides links to questions sent in to Dr. Math about proofs. Topics covered include what proofs are, how to understand them, and how to build them, and much more. Be sure to click on the links which you believe may be helpful.
Oswego City School District
Regents Exam Prep Center: Writing a Proof: Direct Euclidean Proofs
This site is a look into the world of geometric proofs. You'll learn what a proof is and about the different types of proofs. Try the practice page to check your understanding. Teachers can check out the teacher resources for lesson and...
Other
Platonic Realms: Conic Sections
A proof to show that the square root of two is an irrational number, followed by a shorter and even more beautiful proof.
Oswego City School District
Regents Exam Prep Center: Styles of Proof
Find out the general form for two column proofs, flow proofs, and paragraph proofs here. The site is very brief and discusses each type of proof using the same example.
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).
Sophia Learning
Sophia: Types of Proofs: Lesson 3
This lesson will introduce flow chart proofs, paragraph proofs, and two-column proofs, and explain the similarity and differences between the different types of proofs. It is 3 of 5 in the series titled "Types of Proofs."