6.9 Proofs using coordinate Geometry.notebook
March 10, 2014
6.9 Proofs Using Coordinate Geometry
Objective: Be able to prove theorems using figures in the coordinate plane.
A coordinate proof can be used to prove geometric relationships.
A coordinate proof uses variables to name coordinate of a figure
on a coordinate plane.
To Plan a Coordinate Proof Use this basic framework:
1.) What am I trying to prove? What information do I need or am I given?
2.) What Formula do I need to use?
3.) When I do the math, what does my
answer tell me?
Mar 6­11:59 AM
Use coordinate geometry to prove that the
diagonals of a rectangle are congruent.
Mar 6­12:04 PM
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6.9 Proofs using coordinate Geometry.notebook
March 10, 2014
Use coordinate geometry to prove that the
diagonals of an isosceles trapezoid are congruent.
Mar 6­12:07 PM
Use coordinate geometry to prove that the line
containing the midpoints of two sides of a triangle is
parallel to the third side.
Mar 6­12:08 PM
2
6.9 Proofs using coordinate Geometry.notebook
March 10, 2014
Use coordinate geometry to prove that the segments
joining the midpoints of a rectangle form a rhombus.
Mar 6­12:08 PM
Sometimes the most difficult part of coordinate proofs is knowing where to begin. State whether you can reach each conclusion using
coordinate methods. Give a reason for your answer.
1. AB = 1/2CD
2.
ABC is equilateral
3. The diagonals of a quadrilateral form right angles.
4.
ABC is a right triangle
Mar 6­12:09 PM
3
6.9 Proofs using coordinate Geometry.notebook
March 10, 2014
Complete the worksheet: 6.9 Think about a plan with a partner.
Mar 6­12:14 PM
Homework:
6.9 Practice wks
Mar 6­12:16 PM
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