1. A coordinate proof is a style of proof that uses coordinate geometry and algebra. The first step of a coordinate proof is to position the given figure in the plane. You can use any position, but using coordinates with zeros or the figure’s symmetry can make the proof simpler.

2. Formulas for Coordinate Proofs

3. Coordinate Proofs with Variables
A coordinate proof can also be used to prove that a certain relationship is always true.
You can prove that a statement is true for all right triangles without knowing the side lengths.
To do this, assign variables as the coordinates of the vertices.
If a coordinate proof requires calculations with fractions, choose coordinates that are multiples of the denominator.

4. Examples from the Workbook
Pages 173 – 175 examples 1-2
Pages 175 – 176 Practice 2 & 4
Page 177 #1 – 3

5. Example 3
Write a coordinate proof showing that the area of ∆ADB is one half the area of ∆ABC.

6. 4-8 Honors Assignments
Primary assignment: join.quizizz.com
Codes expire at 7AM on the due date
Period (due Thursday)
Period (due Thursday)
Period (due Friday)
Secondary Assignment: Workbook pg 178 ALL

7. 4-8 Assignments
Primary assignment: join.quizizz.com
Codes expire at 7AM on the due date
Period (due Friday)
Period (due Friday)
Period (due Thursday)
Secondary Assignment: Workbook pg 178 ALL