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Two Column Proofs - Concept 32,428 views

Teacher/Instructor Brian McCall
Brian McCall

Univ. of Wisconsin
J.D. Univ. of Wisconsin Law school

Brian was a geometry teacher through the Teach for America program and started the geometry program at his school

Two column proofs are organized into statement and reason columns. Each statement must be justified in the reason column. Before beginning a two column proof, start by working backwards from the "prove" or "show" statement. The reason column will typically include "given", vocabulary definitions, conjectures, and theorems.

One of the scariest parts of Geometry is two column proofs. The reason why it's too difficult it's because often can take everything that that you're trying to say and organize it into 2 columns. One for statement and one reason, so every statement that you make has to have a reason and that's going to be given linear angle, vertical angles reflexive property something like that so every time you make a statement you have to back it up. You're basically like an attorney in the trial case.
Couple of other keys you want to remember always start by giving your reasons you can't make a conclusion without giving your evidence so once you've given your reasons, then you need to draw a conclusion. If you want to you could work backwards. What you're going to what you're being asked to prove or show depending on what your textbook might use for its vernacular will be the last line so the last thing that you're always going to write for your 2 column proof is whatever you're being asked to prove or to show so keep those 3 things in mind and you're always get an a+ on your two column proofs.