National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Two Column Proofs
A response to an inquiry of how to prove a two column geometric proof problem at the Math Forum. This site gives a description of what a makes a proof and an example of a two column proof.
National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Building Two Column Proofs
Use this site to find details of how to construct a two column proof. Dr. Math responds to a question posed by a student and details the reasons for the order of steps and shows two different ways to do the same proof.